MEDIA METRIX INC
424B4, 1999-05-07
BUSINESS SERVICES, NEC
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<PAGE>
                                             As filed Pursuant to Rule 424(b)(4)
                                            Registration Statement No. 333-72883
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
PROSPECTUS
 
MAY 7, 1999
 
                                     [LOGO]
 
                        3,000,000 SHARES OF COMMON STOCK
- ----------------------------------------------------------------------
 
THE COMPANY:                       THE OFFERING:
- - We provide Internet audience     - We are offering 3,000,000 shares
  measurement products and           of our common stock.
  services.                        - The underwriters have an option
- - Media Metrix, Inc.                 to purchase an additional 250,000
  35 East 21(st) Street              shares from Media Metrix and
  New York, New York 10010           200,000 shares from existing
  (212) 460-7980                     stockholders to cover over-
SYMBOL & MARKET:                     allotments.
- - MMXI/Nasdaq National Market      - This is our initial public
                                     offering, and no public market
                                     currently exists for our shares.
                                   - We plan to use the proceeds from
                                     this offering for international
                                     expansion, new product
                                     development, to redeem shares of
                                     redeemable preferred stock held
                                     by The NPD Group, Inc. in the
                                     amount of approximately $4.8
                                     million, and for general
                                     corporate purposes, including
                                     working capital.
                                   - Closing: May 12, 1999
 
<TABLE>
<CAPTION>
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                                                        Per Share      Total
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<S>                                                    <C>          <C>
Public offering price:                                  $   17.00   $51,000,000
Underwriting fees:                                           1.19     3,570,000
Proceeds to Media Metrix:                                   15.81    47,430,000
- -------------------------------------------------------------------------------
</TABLE>
 
     THIS INVESTMENT INVOLVES RISK. SEE "RISK FACTORS" BEGINNING ON PAGE 7.
- --------------------------------------------------------------------------------
 
NEITHER THE SEC NOR ANY STATE SECURITIES COMMISSION HAS DETERMINED WHETHER THIS
PROSPECTUS IS TRUTHFUL OR COMPLETE. NOR HAVE THEY MADE, NOR WILL THEY MAKE, ANY
DETERMINATION AS TO WHETHER ANYONE SHOULD BUY THESE SECURITIES. ANY
REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.
- --------------------------------------------------------------------------------
DONALDSON, LUFKIN & JENRETTE
 
                         BANCBOSTON ROBERTSON STEPHENS
 
                                                      THOMAS WEISEL PARTNERS LLC
 
            THE UNDERSIGNED ARE FACILITATING INTERNET DISTRIBUTION.
 
              DLJDIRECT INC.                     E*TRADE SECURITIES
<PAGE>
Media Metrix: The Power of Relevant Knowledge The Source for Internet Audience
Measurement Data Enabling the Continued Growth and Development of the Internet
 
[Graphic Showing click-by-click details from two panelists' data logs.]
 
Quote from The New York Times
 
[Graphic of four computer screens on gatefold. First screen in top left corner
has picture of Top Rankings list from the Media Metrix Web site. Second screen
in top right corner has picture of a press release captioned "Media Metrix
Releases Results of '98 Holiday Shopping Season." Third screen in middle right
of page shows Web Report: Travel/Tourism. Fourth screen in middle bottom shows a
site analysis report from the Media Metrix Web site.]
 
Text to left of first screen: Audience Measurement. Media Metrix measures the
entire Internet, including the Web and proprietary online services like America
Online.
 
Text to right of second screen: E-Commerce. E-Commerce growth, like that of
Internet advertising, will depend largely on the availability of reliable,
comprehensive quantitative and qualitative data.
 
Text above third screen: Competitive Intelligence. Media Metrix's in depth
clickstream data provides market and competitive intelligence to companies
competing in the digital age.
 
Text to the right of fourth screen: Ad Buying and Selling. Media Metrix audience
measurement data are used as a basis for buying and selling Internet
advertising.
 
Text middle left of page: Setting the Standard. Media Metrix provides Internet
audience measurement products and services to leading Internet advertisers and
advertising agencies, Internet properties, technology companies and financial
institutions.
 
[Graphic in center of page is a three dimensional axis.]
 
    One spoke ends in caption "What We Deliver." Listed along axis are, in order
from center: audience measurement, e-commerce data, demographic segmentation,
custom analysis and technology usability. Arrow points from "audience ratings"
on spoke to fourth screen.
 
    Second spoke ends in "What We Measure." Listed along axis are, in order from
center: software and hardware, digital media, Internet, online services and
world wide web. Arrow points from "internet" on axis to first screen.
 
    Third axis ends in "Who Uses It." Listed on axis are, in order from center:
technology companies, financial analysts, web sites, ad agencies, e-commerce
marketers and media organizations. Arrow points from "financial analysts" on
axis to third screen. Arrow points from "e-commerce marketers" on axis to second
screen.
 
    Logo in lower left corner.
<PAGE>
                               TABLE OF CONTENTS
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                                                   PAGE
<S>                                             <C>
Prospectus Summary............................           4
Risk Factors..................................           7
Use of Proceeds...............................          20
Dividend Policy...............................          20
Capitalization................................          21
Dilution......................................          22
Selected Financial Data.......................          23
Management's Discussion and Analysis of
  Financial Condition and Results of
  Operations..................................          24
Business......................................          33
Management....................................          45
 
<CAPTION>
                                                   PAGE
<S>                                             <C>
Certain Relationships and Related
  Transactions................................          51
Principal and Selling Stockholders............          54
Description of Capital Stock..................          58
Shares Eligible for Future Sale...............          62
Underwriting..................................          64
Legal Matters.................................          67
Experts.......................................          67
Where You Can Find Additional Information.....          67
Index to Financial Statements.................         F-1
</TABLE>
 
                                       3
<PAGE>
                               PROSPECTUS SUMMARY
 
    THE INFORMATION BELOW IS ONLY A SUMMARY OF MORE DETAILED INFORMATION
INCLUDED IN OTHER SECTIONS OF THIS PROSPECTUS. THE OTHER INFORMATION IS
IMPORTANT, SO PLEASE READ THIS ENTIRE PROSPECTUS CAREFULLY. UNLESS STATED
OTHERWISE, THE INFORMATION CONTAINED IN THIS PROSPECTUS ASSUMES THAT THE
UNDERWRITERS' OVER-ALLOTMENT OPTION IS NOT EXERCISED AND GIVES EFFECT TO A
1.4648-FOR-ONE SPLIT OF OUR COMMON STOCK.
 
                                  MEDIA METRIX
 
OUR BUSINESS
 
    We provide Internet audience measurement products and services to leading
Internet advertisers and advertising agencies, Internet properties, technology
companies and financial institutions. We measure usage of the entire Internet,
including its largest segments, the World Wide Web and proprietary on-line
services like America Online. Our products and services enable the continued
growth and development of the Internet by providing third-party audience
measurement data that our customers rely on to make critical business decisions.
 
    We collect data by measuring Internet usage from a representative sample, or
panel, of personal computer users with our proprietary tracking technology. We
maintain a large panel of Internet users reporting Internet usage at work and at
home, as well as the usage of proprietary on-line services. Our audience
measurement methodology has been developed from our background in marketing and
media research, particularly our experience with recruiting and operating
panels. Each panelist is required to fill out a detailed questionnaire to
provide background demographic information. Our proprietary tracking technology
collects data from the panelist's personal computer and transmits these data to
our office for processing. The data are then used to construct several
databases, which we use to provide our products and services.
 
    We have been at the forefront of the development and coordination of
technology and standards needed to facilitate advertising and transactions
between companies doing business over the Internet. Our customers include
Amazon.com, America Online, Beyond.com, Buena Vista/Disney, eBay, Everen
Securities, Fidelity, IBM, Infoseek, Interpublic Group, Microsoft, Omnicom, Time
Warner, Xoom.com and Yahoo! The quality and depth of our customer base and our
customer renewal rate of over 95% reflect our position as a widely accepted
Internet audience measurement service.
 
OUR MARKET OPPORTUNITY
 
    Advertising is a critical revenue stream for providers of Internet content
and services. As Web sites and on-line content providers seek to increase
advertising revenues, and as on-line advertisers seek to determine where they
should spend their marketing dollars, demand is growing for reliable statistics
and standardized methods to evaluate Internet usage. As a result, a standard for
Internet audience measurement must emerge which will:
 
    - measure a large and representative sample of Internet users;
 
    - track activity on the entire Internet, not just the Web, so that key
      properties like America Online and other proprietary on-line services and
      technologies are included;
 
    - measure the Internet audience both at work and at home, because Internet
      usage differs in these two environments; and
 
    - be unbiased and independent from advertisers and content providers.
 
                                       4
<PAGE>
OUR STRATEGY
 
    Our goal is to become the accepted standard for Internet audience
measurement. We intend to achieve this goal through the following strategies:
    - continue our industry leadership;
    - develop products to accelerate e-commerce growth;
    - expand and increase penetration of our client base;
    - expand internationally; and
    - develop new products and services.
 
OUR HISTORY
 
    Our business was originally conducted as a division within The NPD Group,
Inc., a leading marketing research firm. In March 1996, NPD formed PC Meter, a
Delaware limited partnership, to conduct our business. In March 1997, we
reorganized into a Delaware corporation and began using the trade name Media
Metrix in our business. In November 1998, we merged with RelevantKnowledge,
Inc., our leading competitor. NPD, our largest stockholder and parent, will own
approximately 26.2% of our common stock following this offering.
 
    Although our revenues have continued to grow, we have a history of operating
losses and negative cash flow. In addition, the market for Internet audience
measurement services is new and rapidly evolving, and we expect competition in
this market to intensify in the future.
 
    Our principal executive offices are located at 35 East 21(st) Street, New
York, New York 10010, and our telephone number is (212) 460-7980.
 
    Media Metrix, PC Meter, RelevantKnowledge, E-Trends, The Power of Relevant
Knowledge and the Media Metrix logo are our trademarks. Any other trademark,
trade name or service mark of any other company appearing in this prospectus
belongs to its holder.
 
                                  THE OFFERING
 
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<S>                                            <C>
Common stock offered by Media Metrix.........  3,000,000 shares
Common stock to be outstanding after the
  offering...................................  16,727,828 shares
Use of proceeds..............................  We intend to use the net proceeds from this
                                               offering to fund international expansion, new
                                               product development, the redemption of our
                                               outstanding redeemable preferred stock and
                                               for general corporate purposes, including
                                               working capital.
Nasdaq National Market Symbol................  MMXI
</TABLE>
 
The outstanding share information is based on our shares outstanding as of March
31, 1999. This information excludes:
    - 462,907 shares of common stock subject to options granted under our 1998
      Equity Incentive Plan and outstanding as of March 31, 1999 at a weighted
      average exercise price of $7.47 per share;
    - 496,283 shares of common stock subject to options granted under our
      earlier Stock Option Plan and outstanding as of March 31, 1999 at a
      weighted average exercise price of $0.84 per share;
    - 854,648 additional shares of common stock reserved for issuance under our
      1998 Equity Incentive Plan; and
    - 469,413 shares of common stock reserved for outstanding warrants at a
      weighted average exercise price of $1.87 per share.
 
                                       5
<PAGE>
                             SUMMARY FINANCIAL DATA
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)
 
    The following table summarizes the statement of operations data for our
business and our predecessor business. The pro forma data give effect to our
merger with RelevantKnowledge as if it took place on January 1, 1998. For a more
detailed explanation of these financial data, see "Selected Financial Data" and
our financial statements located elsewhere in this prospectus.
 
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<CAPTION>
                                  PERIOD FROM                                                   THREE MONTHS ENDED
                                   INCEPTION              YEAR ENDED              PRO FORMA
                                    THROUGH              DECEMBER 31,             YEAR ENDED        MARCH 31,
                                 DECEMBER 31,   -------------------------------  DECEMBER 31,  --------------------
                                     1995         1996       1997       1998         1998        1998       1999
<S>                              <C>            <C>        <C>        <C>        <C>           <C>        <C>
STATEMENT OF OPERATIONS DATA:
Revenues.......................    $      --    $   1,033  $   3,188  $   6,331   $    8,145   $   1,160  $   3,178
Gross profit (loss)............         (140)        (711)      (275)     2,210        1,145         360      1,458
Loss from operations...........         (372)      (3,376)    (4,679)    (7,223)     (16,058)       (897)    (2,463)
Net loss applicable to common
  stockholders.................         (372)      (3,376)    (4,874)    (7,472)     (16,211)       (929)    (2,466)
 
Basic and diluted net loss per
  common share applicable to
  common stockholders..........    $   (0.06)   $   (0.52) $   (0.75) $   (0.98)  $    (1.49)  $   (0.14) $   (0.19)
 
Shares used in calculating
  basic and diluted net loss
  per common share applicable
  to common stockholders.......        6,523        6,523      6,523      7,619       10,861       6,523     13,296
</TABLE>
 
    The following balance sheet data give effect to our sale of 3,000,000 shares
of common stock in this offering at the initial public offering price of $17.00
per share, after deducting the underwriting discount and estimated offering
expenses, and the application of net proceeds from this offering.
 
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<CAPTION>
                                                                                           AS OF MARCH 31, 1999
                                                                                         -------------------------
                                                                                          ACTUAL     AS ADJUSTED
<S>                                                                                      <C>        <C>
BALANCE SHEET DATA:
Cash and cash equivalents..............................................................  $   2,385    $   44,132
Working capital........................................................................        312        42,189
Total assets...........................................................................     11,240        52,778
Redeemable preferred stock.............................................................      4,762            --
Total stockholders' equity.............................................................      1,474        47,904
</TABLE>
 
                                       6
<PAGE>
                                  RISK FACTORS
 
    BEFORE YOU INVEST IN OUR COMMON STOCK, YOU SHOULD BE AWARE OF VARIOUS RISKS,
INCLUDING THOSE DESCRIBED BELOW. YOU SHOULD CAREFULLY CONSIDER THESE RISK
FACTORS, TOGETHER WITH ALL OF THE OTHER INFORMATION INCLUDED IN THIS PROSPECTUS,
BEFORE YOU DECIDE WHETHER TO PURCHASE SHARES OF OUR COMMON STOCK. ANY OR ALL OF
THESE RISKS COULD HAVE A MATERIAL ADVERSE EFFECT ON OUR BUSINESS, RESULTS OF
OPERATIONS OR FINANCIAL CONDITION. THE RISKS SET OUT BELOW MAY NOT BE
EXHAUSTIVE. KEEP THESE RISK FACTORS IN MIND WHEN YOU READ FORWARD-LOOKING
STATEMENTS ELSEWHERE IN THIS PROSPECTUS. THESE ARE STATEMENTS THAT RELATE TO OUR
EXPECTATIONS FOR FUTURE EVENTS AND TIME PERIODS. GENERALLY, THE WORDS
"ANTICIPATE," "EXPECT," "INTEND" AND SIMILAR EXPRESSIONS IDENTIFY
FORWARD-LOOKING STATEMENTS. FORWARD-LOOKING STATEMENTS INVOLVE RISKS AND
UNCERTAINTIES, AND FUTURE EVENTS AND CIRCUMSTANCES COULD DIFFER SIGNIFICANTLY
FROM THOSE ANTICIPATED IN THE FORWARD-LOOKING STATEMENTS.
 
WE DO NOT HAVE A LONG OPERATING HISTORY.
 
    We began our operations as a division of NPD in October 1995. We have only
operated as an entity independent of NPD since March 31, 1996. Our operating
history is therefore limited. In addition, we recently merged with
RelevantKnowledge and have been operating as one company only since early
November 1998.
 
    You must consider the risks and difficulties frequently encountered by
early-stage companies in new and rapidly evolving markets. Some of these risks
and uncertainties relate to our ability to:
 
    - anticipate and adapt to our evolving market;
 
    - implement sales and marketing initiatives;
 
    - enhance the Media Metrix brand;
 
    - attract, retain and motivate qualified personnel;
 
    - respond to actions taken by our competitors;
 
    - effectively manage our growth by building a solid base of operations and
      technology; and
 
    - integrate acquired businesses, consumer panels, technologies and services.
 
    We cannot assure you that we will be successful in addressing these risks
and uncertainties. Our failure to do so could have a material adverse effect on
our business, results of operations and financial condition.
 
WE HAVE A HISTORY OF OPERATING LOSSES AND NEGATIVE CASH FLOW.
 
    Our ability to generate significant revenues is uncertain. Although our
revenues have continued to grow, we are not yet profitable. We incurred losses
from operations of $3.4 million in 1996, $4.7 million in 1997, $7.2 million in
1998 and $2.5 million in the three months ended March 31, 1999. We expect our
operating and net losses to continue. If the merger with RelevantKnowledge had
taken place on January 1, 1998, our pro forma loss from operations for 1998
would have been $16.1 million. Our ability to generate profits in the future
will depend on a number of factors, including:
 
    - maintaining and enhancing our position as the leading Internet audience
      measurement service;
 
    - keeping our costs in line with our budget;
 
    - retaining our existing customers;
 
    - increasing our sales to existing customers;
 
    - obtaining new customers;
 
                                       7
<PAGE>
    - increasing business and consumer acceptance of the Internet as a source of
      information and as a place to buy and sell goods and services;
 
    - the growth of advertising and e-commerce on the Internet;
 
    - regulation of the Internet by Federal or local governments;
 
    - the health of the general economy; and
 
    - economic conditions that uniquely affect the Internet.
 
    We intend to invest heavily in our technologies, additional products and
services and international expansion. As a result, we will need to achieve
significant revenue increases to achieve and maintain profitability. Although
our revenues and the number of our clients have continued to increase, we may
not be able to continue to grow and to expand our business. The number of
clients or the number of products and services for which our clients subscribe
may grow more slowly than we anticipate or may decrease in the future. Even if
we become profitable, we may not sustain or increase our profits on a quarterly
or annual basis in the future.
 
THE INTERNET AUDIENCE MEASUREMENT INDUSTRY IS NEW AND RAPIDLY EVOLVING.
 
    To date, no Internet audience measurement service has been adopted as the
universally accepted standard. Our existing and potential customers may
challenge or refuse to accept our audience measurement reports. Our customers
may be dissatisfied with our methodology for measuring Internet audiences or may
feel that our panel is not representative of Internet users. Furthermore,
another Internet audience measurement service may be adopted as the industry
standard. As a result, our customers may turn to alternative services provided
by current or potential competitors.
 
WE DEPEND ON CONTINUED GROWTH IN USE OF THE INTERNET.
 
    Our business would be adversely affected if Internet usage for the exchange
of information and for commerce does not continue to grow rapidly. Internet
usage may be inhibited for a number of reasons, including:
 
    - inadequate network infrastructure;
 
    - security concerns;
 
    - inconsistent quality of service; or
 
    - lack of availability of cost-effective, high-speed service.
 
    Even if Internet usage grows, the Internet infrastructure may not be able to
support the demands placed on it by this growth. As a result, its performance
and reliability may decline. In addition, Web sites and proprietary on-line
services have experienced interruptions in their service as a result of outages
and other delays occurring throughout their infrastructure. If these outages or
delays frequently occur in the future, Internet usage as a medium for the
exchange of information and for commerce could grow more slowly or decline.
 
THE ACCEPTANCE AND EFFECTIVENESS OF INTERNET ADVERTISING IS UNPROVEN.
 
    Our future success will depend on an increase in the use of the Internet as
an advertising medium. The Internet advertising market is new and rapidly
evolving. It cannot yet be compared with the traditional advertising market to
gauge its effectiveness. As a result, there is significant uncertainty about the
demand and market acceptance for Internet advertising. Many of our current or
potential customers have little or no experience using the Internet for
advertising purposes. The adoption of
 
                                       8
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Internet advertising, particularly by entities that have historically relied on
traditional media for advertising, requires the acceptance of a new way of
conducting business. These companies may find Internet advertising to be less
effective for promoting their products and services as compared to traditional
advertising. In addition, most current and potential Web publisher customers
have little or no experience in generating revenues from the sale of advertising
space on their Web sites. We cannot assure you that the market for Internet
advertising will continue to emerge or will become sustainable. If the market
for Internet advertising fails to develop or develops more slowly than we
expect, then our business, results of operations and financial condition could
be materially and adversely affected.
 
WE MAY FAIL TO SUCCESSFULLY INTEGRATE RELEVANTKNOWLEDGE.
 
    We recently merged with RelevantKnowledge. Our success will depend, in part,
on our ability to fully integrate the operations and management of
RelevantKnowledge. A successful integration requires, among other things, the
integration of RelevantKnowledge's product offerings and technology into ours
and the coordination of their research and development, sales and marketing and
financial reporting efforts with ours. We cannot assure you that we will
accomplish the integration smoothly or successfully. We cannot assure you that
we will realize the anticipated benefits of the RelevantKnowledge merger. The
success of the integration will require the dedication of management and other
personnel resources which may temporarily distract their attention from our
day-to-day business.
 
OUR OPERATING RESULTS MAY FLUCTUATE FROM QUARTER TO QUARTER.
 
    Our operating results have varied from quarter to quarter. Our operating
results may continue to vary as a result of a variety of factors. These factors
include:
 
    - our ability to retain our current clients;
 
    - our ability to sell additional products and services to current clients;
 
    - our ability to attract new clients;
 
    - our ability to maintain customer satisfaction;
 
    - the announcement or introduction of new products and services by us or our
      competitors;
 
    - price competition;
 
    - our ability to upgrade and to develop our systems and infrastructure to
      accommodate our growth;
 
    - our ability to attract new personnel;
 
    - the timing, cost and availability of advertising in traditional media;
 
    - the impact of possible acquisitions both on our operations and on our
      reported operating results due to associated accounting charges;
 
    - technical difficulties or service interruptions;
 
    - the amount and timing of costs relating to changes in the size or
      composition of our panel; and
 
    - the amount and timing of operating costs and capital expenditures relating
      to expansion of our business, including our planned international
      expansion.
 
    Many of these factors are beyond our control. We cannot assure you that our
revenues will increase in proportion to the increase in advertising on the
Internet, or at all. In addition, we cannot assure you that advertising on the
Internet will continue to grow at forecasted levels, or at all. A substantial
portion of our current and future costs are fixed. If our revenues fall short of
expectations, we may not be able to adjust our fixed expenses to compensate for
this shortfall on a timely basis.
 
                                       9
<PAGE>
Further, as a strategy for remaining competitive, we may have to make certain
pricing, service or marketing decisions that could have a material adverse
effect on our business, results of operations and financial condition.
 
    Due to these factors, period-to-period comparisons of our revenues and
operating results are not necessarily meaningful. Therefore, you should not rely
on these comparisons as indicators of our future performance. We also cannot
assure you that we will be able to:
 
    - sustain the rates of revenue growth we have experienced in the past;
 
    - improve our operating results; or
 
    - sustain our profitability on a quarterly basis.
 
    In addition, our operating results in future periods may be below the
expectations of securities analysts and investors. If that occurs, the market
price of our common stock could be materially and adversely affected.
 
WE OPERATE IN HIGHLY COMPETITIVE MARKETS.
 
    The market for Internet audience measurement services is new and rapidly
evolving. We expect competition in this market to intensify in the future. One
of our competitors, NetRatings, Inc., announced a strategic relationship with
Nielsen Media Research, Inc. in October 1998. In March 1999, NetRatings and
Nielsen Media Research introduced a new Web site ratings service that competes
directly with many aspects of our services. Nielsen Media Research is the
leading provider of television audience measurement services and has
significantly more financial and other resources than do we. In light of these
events, it is likely that the Nielsen/NetRatings venture will become a
significant competitor.
 
    We also compete indirectly with operators of site-centric and other
consumer-centric measurement systems. Site-centric measurement systems measure
audience visits at a specific Web site by monitoring the Web site's server.
Consumer-centric systems measure the market either in a manner similar to us or
qualitatively through on-line and telephonic interviews.
 
    In addition, we may face competition from individual Web sites that develop
an independent method of measuring their own audience or from other companies
that develop alternative audience measurement technologies to those already
provided by us.
 
    Competitive pressures could have a material adverse effect on our business,
results of operations and financial condition. We believe that the principal
competitive factors in our market are:
 
    - creating representative consumer and business panels; and
 
    - providing audience measurement services for the entire Internet, including
      the Web and proprietary on-line services.
 
    Some of our competitors have:
 
    - longer operating histories;
 
    - larger customer bases;
 
    - greater brand recognition in similar businesses; and
 
    - significantly greater financial, marketing, technical and other resources.
 
    In addition, some of our competitors may be able to:
 
    - devote greater resources to marketing and promotional campaigns;
 
                                       10
<PAGE>
    - adopt more aggressive pricing policies; and
 
    - devote substantially more resources to technology and systems development.
 
    Increased competition may result in reduced operating margins, loss of
market share and diminished value in our services, as well as different pricing,
service or marketing decisions. We cannot assure you that we will be able to
compete successfully against current and future competitors.
 
WE FACE MANY CHALLENGES IN CONNECTION WITH OUR PLANNED INTERNATIONAL EXPANSION.
 
    Our current strategy includes expansion of our services to measure Internet
audiences outside of the United States. Our expansion into international markets
will require management attention and resources. The international markets for
audience measurement services have historically been extremely localized and
difficult to penetrate. We cannot assure you that we will be able to develop new
products and services based on data obtained in those markets. We cannot assure
you that we will be successful in marketing our products and services to clients
in markets outside the United States. In addition, our international operations
will be subject to a number of inherent risks, including:
 
    - the impact of recessions in economies outside the United States;
 
    - changes in regulatory requirements;
 
    - reduced protection for intellectual property rights in some countries;
 
    - potentially adverse tax consequences;
 
    - economic and political instability; and
 
    - fluctuations in currency exchange rates.
 
    These risks may have a material adverse effect on our business, results of
operations or financial condition.
 
WE WILL DEPEND ON STRATEGIC RELATIONSHIPS IN INTERNATIONAL MARKETS.
 
    The success of our international expansion will depend on our ability to:
 
    - recruit and maintain at-home and at-work panels that are representative of
      a geographic area;
 
    - control costs and effectively manage foreign operations; and
 
    - effectively market and sell any new products or services.
 
    These challenges require skills and expertise in foreign countries that we
do not currently have. We believe that our success in penetrating markets
outside of the United States will depend on our ability to develop and to
maintain strategic relationships with local audience measurement or marketing
research companies. If we do not succeed in attracting or retaining strategic
partners in markets outside the United States, our business, financial condition
and results of operations could be materially adversely affected.
 
OUR MARKET IS SUBJECT TO RAPID CHANGE.
 
    Our market is characterized by:
 
    - rapidly changing technology;
 
    - evolving industry standards;
 
    - introductions and enhancements of competitive products and services; and
 
    - changing customer demands.
 
                                       11
<PAGE>
    Accordingly, our future success depends on our ability to:
 
    - adapt to rapidly changing technologies;
 
    - adapt our services to evolving industry standards; and
 
    - improve the features, reliability and timeliness of our product and
      service offerings in response to competitive product and service offerings
      and evolving demands of the marketplace.
 
    We cannot assure you that we will succeed in addressing these issues. In
addition, the widespread adoption of new Internet networking technologies or
other technological changes could require us to expend substantial amounts of
capital to change our services or infrastructure. These changes may also involve
new technologies that may not be measurable by our current methods.
 
OUR COSTS MAY INCREASE IF THE SIZE OR COMPOSITION OF OUR PANEL CHANGES.
 
    A significant portion of our costs consists of the expense of recruiting and
maintaining our panel and collecting and processing data generated by the panel.
We may, in the future, need to change the size or composition of our panel. As a
result, our expenses for recruiting and maintaining our panel may increase. This
could have a material adverse effect on our business, results of operations and
financial condition.
 
WE MAY NOT BE ABLE TO EFFECTIVELY MANAGE OUR INTERNAL GROWTH.
 
    We are currently experiencing a period of rapid expansion. We anticipate
that future expansion will be necessary in order to accommodate our needs and to
take advantage of new opportunities in the market for audience measurement
services on the Internet. In order to succeed, we will need to attract and hire
additional technical and management personnel. As a result, we expect to add key
personnel in the near future to manage our expected growth. We also will need to
expand our technical, finance, administrative and operations staff. We cannot
assure you that current and planned personnel, systems, procedures and controls
will be adequate to support our future operations. We may not be able to hire
and retain our personnel. We also may not be able to exploit existing and
potential strategic relationships and market opportunities. If we fail to
effectively manage our internal growth, our business, results of operations and
financial condition could be materially adversely affected.
 
WE DEPEND ON RENEWALS OF OUR SUBSCRIPTION BASED SERVICES.
 
    We have historically derived substantially all of our revenues from
subscriptions for our syndicated products. In our limited history, high renewal
rates have formed a foundation for our revenue growth. However, we cannot assure
you we will continue to experience high renewal rates. Our subscription renewal
rates may also decline as a result of a consolidation in our customer base or if
a significant number of our customers cease operations. If our renewal rate
percentage declines, it could have a material adverse effect on our business,
results of operations and financial condition.
 
WE MUST FURTHER DEVELOP OUR BRAND NAME.
 
    We believe that maintaining and strengthening the Media Metrix brand is an
important aspect of our business. Our brand name is critical in our efforts to
attract clients. We believe that the importance of brand recognition will
increase due to the increasing number of competitors entering the market for
Internet audience measurement. Our ability to promote and position the Media
Metrix brand depends largely on:
 
    - the success of our marketing efforts; and
 
    - our ability to provide our customers with high quality products.
 
                                       12
<PAGE>
    To promote the Media Metrix brand in response to competitive pressures, we
may find it necessary to increase our marketing budget or otherwise increase our
financial commitment to creating and maintaining brand loyalty among our
clients. If we fail to promote and maintain our brand, or incur excessive
expenses attempting to promote and maintain our brand, our business, results of
operations and financial condition will be materially adversely affected.
 
WE MAY ENCOUNTER RISKS ASSOCIATED WITH NEW PRODUCT DEVELOPMENT.
 
    Our future success depends in part on our ability to offer new products and
services on a timely and cost-effective basis. In order to gain market
acceptance, our new products and services must address:
 
    - specific industries and businesses;
 
    - changes in client requirements; and
 
    - changes in technologies.
 
    The process of developing and launching new products or services is
inherently risky and costly. Moreover, we cannot assure you that once launched,
our products and services will be accepted by our customers.
 
OUR SYSTEMS MAY FAIL.
 
    Our success depends on the efficient and uninterrupted operation of our
computer and communications systems. Some personal computers, servers and
portions of our network are provided to us by NPD under a management services
agreement. NPD also provides us with the use of mini-computers that we use to
process data received from panelists. Later this year, we plan to separate our
systems from those of NPD and to construct an independent network. Any failure
of the current or the new networks could impede the processing of data, customer
orders and day-to-day management of our business. This could have a material
adverse effect on our business, results of operations and financial condition.
 
    Our systems and operations are vulnerable to damage or interruption from:
 
    - telecommunication failures;
 
    - power loss;
 
    - fires;
 
    - floods;
 
    - physical and electronic break-ins;
 
    - sabotage; and
 
    - intentional acts of vandalism and similar events.
 
    We do not presently have fully redundant systems. Despite any precautions we
take, a natural disaster or other unanticipated problems which lead to the
corruption or loss of data at the NPD facility or our own facilities could
result in interruptions in the services we provide. In addition, our data bases
are growing rapidly, and the systems currently in place may not be sufficient to
handle any further expansion. This could lead to systems failure or to a
corruption of our data and could have a material adverse effect on our business,
results of operations and financial condition.
 
                                       13
<PAGE>
WE DEPEND ON OUR KEY PERSONNEL.
 
    Our future success depends on the continued services and on the performance
of our senior management and other key employees, in particular the services of
Tod Johnson, our Chief Executive Officer. Mr. Johnson also serves as the Chief
Executive Officer of NPD. We anticipate Mr. Johnson will spend a substantial
portion of his time on our matters. However, he will not be able to devote all
of his time to our affairs. As a result, Mr. Johnson's other responsibilities
could divert his attention from our affairs.
 
    Our performance depends on our ability to retain and to motivate our key
employees. The loss of the services of any of our key employees could have a
material adverse effect on our business, results of operations and financial
condition. We do not have long-term employment agreements with any of our key
personnel. We do not maintain any "key person" life insurance policies. In
addition, we are likely to need to recruit additional senior management
personnel as our business grows, particularly in the international arena. Our
future success depends on our ability to hire and to retain highly skilled
personnel. Competition for these candidates is intense. We cannot assure you
that we will be able to successfully attract, integrate or retain sufficiently
qualified personnel. Our inability to retain and attract the necessary personnel
could have a material adverse effect on our business, results of operations and
financial condition.
 
WE MAY FAIL TO INTEGRATE ACQUISITIONS.
 
    If appropriate opportunities present themselves, we intend to acquire other
complementary businesses, technologies, services or products. We currently have
no understandings or agreements relating to any acquisition. We cannot assure
you that we will be able to complete future acquisitions successfully or to
integrate an acquired entity with our current business. An acquisition may
result in unforeseen operating difficulties and expenditures. They may also
require significant management attention that would otherwise be available for
ongoing development of our business. Moreover, we cannot assure you that the
anticipated benefits of any acquisition will be realized. We may:
 
    - issue additional equity securities which would dilute stockholders;
 
    - incur debt;
 
    - incur contingent liabilities; and
 
    - incur amortization expenses related to goodwill and other intangible
      assets.
 
WE DEPEND ON THE NPD GROUP, INC.
 
    We were originally formed as a division of NPD. Throughout our development,
we have relied on services and financing provided to us by NPD. When we became
an independent operating entity, we entered into a management services
agreement, license agreement and services agreement with NPD. These agreements
allow us to continue to use some of NPD's software and services on an as-needed
basis. Under the management services agreement, NPD provides us with managerial
services. Under the license agreement, we license some of NPD's technologies
necessary for the operation of our services. The services agreement provides for
payment of a licence fee by NPD for access to information collected from our
panel.
 
    NPD may be able to exert influence over our business and affairs due to
these arrangements. Also, the loss of the services provided by NPD under the
management services agreement or the loss of the license of computer software
under the license agreement could have a material adverse effect on our
business, financial condition and results of operations. See "Certain
Transactions--Transactions with Directors and Executive Officers."
 
                                       14
<PAGE>
WE MAY NOT BE ABLE TO PROTECT AND ENFORCE OUR INTELLECTUAL PROPERTY RIGHTS.
 
    We regard the protection of our patents, copyrights, service marks,
trademarks and trade secrets as important to our future success. We rely on a
combination of patent, copyright, trademark, service mark and trade secret laws
and contractual restrictions to establish and protect our proprietary rights. We
have entered into confidentiality and invention assignment agreements with our
employees and contractors, and nondisclosure agreements with parties we do
business with in order to limit access to and disclosure of our proprietary
information. We cannot assure you that these contractual arrangements or the
other steps we have taken will be sufficient to protect our intellectual
property from infringement or misappropriation. Moreover, others may
independently develop similar or superior technologies.
 
    We seek to obtain the issuance of patents and the registration of our
trademarks and service marks in the United States and in selected other
countries. We cannot assure you that patents or trademark registrations will be
issued with respect to pending or future applications or that our patents and
trademarks will be upheld as valid. Effective patent, trademark, service mark,
copyright and trade secret protection may not be available in every country in
which our services are offered.
 
    Third parties may claim that our technologies infringe upon their
proprietary rights. We expect that the number of infringement claims in our
market will increase as the number of services and competitors in our industry
grows. These claims, whether meritorious or not, could:
 
    - be time-consuming;
 
    - result in costly litigation; or
 
    - require us to enter into royalty or licensing agreements.
 
    Royalty or licensing agreements might not be available on terms we find
acceptable or at all. As a result, any such claim could have a material adverse
effect upon our business, results of operations and financial condition.
 
WE RELY ON TECHNOLOGY LICENSED FROM NPD AND OTHERS.
 
    We rely on technologies that we license from third parties, like NPD. NPD
licenses to us some key software products and database technologies. We cannot
assure you that these licenses will not infringe on the proprietary rights of
others. We also cannot assure you that these third-party technology licenses
will continue to be available to us on commercially reasonable terms, if at all.
As a result, we may need to obtain substitute technology of lower quality or
performance standards or at greater cost. This could materially adversely affect
our business, results of operations and financial condition.
 
WE MAY BE EXPOSED TO POSSIBLE LIABILITY FOR SUPPLYING INACCURATE INFORMATION TO
  OUR CUSTOMERS.
 
    We may face liability for information that we supply to customers if the
information is inaccurate. The information in our databases, like that in any
database, may contain inaccuracies that our customers may not accept. Any
dissatisfaction by our customers with our measurement methodologies or databases
would have a material adverse effect on our ability to attract new customers and
retain existing customers. Our customer contracts generally provide that each
customer must indemnify us for any damages arising from the use of data, reports
or analyses by the customer or the performance of any consulting, analytic or
other services by us. However, we cannot be certain our contract provisions
provide sufficient protection. Any liabilities which we may incur because of
irregularities or inaccuracies in the data we supply to our customers could
materially adversely affect our business, results of operations and financial
condition.
 
                                       15
<PAGE>
OUR PROPRIETARY RIGHTS MAY BE ADVERSELY AFFECTED BY OUR STRATEGIC PARTNERS.
 
    We expect to license some of our proprietary rights to strategic partners in
the course of our planned international expansion. While we will attempt to
ensure that the quality of our service is maintained by our strategic partners,
we cannot assure you that they will not take actions that might materially
adversely affect the value of our proprietary rights or reputation. This could
have a material adverse effect on our business, results of operations and
financial condition.
 
WE FACE RISKS RELATED TO STORAGE OF PERSONAL INFORMATION ABOUT OUR PANELISTS.
 
    We do not attempt to capture information regarding our panelists' banking,
credit card or password data. This information, however, may come into our
possession. Our panel data are released only in an aggregated format or in a
form not identifiable on an individual basis. However, if someone penetrates our
network security or otherwise misappropriates sensitive data about our
panelists, we could be subject to liability. These liabilities could include
claims for unauthorized purchases with credit card information, impersonation or
other similar fraud claims. They could also include claims for other misuses of
personal information, like for unauthorized marketing purposes. These claims
could result in litigation and could have a material adverse effect on our
business, results of operations and financial condition.
 
WE FACE RISKS OF INDUSTRY INITIATIVES.
 
    Several key industry organizations, including the Internet Advertising
Bureau, the Media Ratings Council, the Advertising Research Foundation and FAST
Forward, have begun initiatives focusing on appropriate standards for Internet
audience measurement. Our products and services may ultimately not comply with
recommended industry guidelines if we determine that compliance would not be
economically feasible or otherwise not consistent with our business strategy. To
the extent that our measurement approach diverges from the course of action
recommended by some or all of these trade groups, our business, results of
operations and financial condition could be materially and adversely affected.
 
THERE ARE RISKS ASSOCIATED WITH YEAR 2000 COMPLIANCE.
 
    Many currently installed computer systems and software products are coded to
accept only two-digit entries in the date code field and cannot reliably
distinguish dates beginning on January 1, 2000 from dates prior to the year
2000. Many companies' software and computer systems may need to be upgraded or
replaced in order to correctly process dates beginning in 2000.
 
    We rely on equipment and software provided by third parties that may not be
year 2000 compliant. The failure of third-party equipment or software to
properly process dates for the year 2000 and any failure by these third parties
to resolve any year 2000 issues could cause us to incur unanticipated expenses.
These expenses could have a material adverse effect on our business, results of
operations and financial condition. Finally, to the extent that year 2000 issues
have a negative impact on consumers and undermine the public's faith in the
Internet as a medium for the exchange of information and commerce, growth of the
Internet could slow. As a result, our business, results of operations and
financial condition could be materially adversely affected.
 
    In addition, we collect our panel data from a diverse group of individual
personal computer users who use a variety of computer hardware and software that
may not be year 2000 compliant. As a result, we may encounter difficulties in
gathering and accurately measuring data from our panel. In addition, it is
possible that data collected from some of these users may contain inaccuracies
resulting from year 2000 issues. These difficulties could have a material
adverse effect on our business, results of operations and financial condition.
See "Management's Discussion and Analysis of Financial Condition and Results of
Operations--Year 2000 Compliance."
 
                                       16
<PAGE>
WE FACE RISKS ASSOCIATED WITH POTENTIAL GOVERNMENTAL REGULATION.
 
    We are currently not subject to direct federal, state or local regulation or
laws or regulations applicable to the Internet, other than regulations
applicable to businesses generally. However, due to the increasing popularity
and use of the Internet, it is possible that a number of laws and regulations
may be adopted covering:
 
    - user privacy;
 
    - freedom of expression;
 
    - pricing;
 
    - content;
 
    - quality of products and services;
 
    - taxation;
 
    - advertising;
 
    - intellectual property rights; and
 
    - information security.
 
    The nature and effect of any proposed legislation or regulation cannot be
fully determined. These could have a material adverse effect on our business,
results of operations and financial condition.
 
    The adoption of any such legislation could also dampen the growth in use of
the Internet generally and decrease its acceptance as a communications,
commercial and advertising medium. Any legislation which could have any adverse
effect on the growth of the Internet could decrease the demand for our services
and could have a material adverse effect on our business, results of operations
and financial condition.
 
THERE MAY BE LIMITS IMPOSED ON USES OF PERSONAL INFORMATION GATHERED USING THE
  INTERNET.
 
    Several states have proposed legislation that would limit the uses of
personal user information gathered using the Internet. These regulations have
required proprietary on-line service and Web site owners to establish privacy
policies. The Federal Trade Commission has also recently settled a proceeding
with one on-line service regarding the manner in which personal information is
collected from users and provided to third parties. Also, the European Union
recently enacted its own privacy regulations that may result in limits on the
collection and use of user information. Because all of our panelists consent to
the retrieval of their personal data, to date these regulations and proceedings
have not impacted our operations. However, changes to existing laws or the
passage of new laws intended to address these issues could, among other effects:
 
    - create uncertainty in the marketplace that could reduce demand for our
      services;
 
    - limit our ability to collect and to use data from our panels;
 
    - increase the cost of doing business as a result of litigation costs or
      increased service delivery costs;
 
    - decrease the efficacy of Internet advertising; or
 
    - in some other manner have a material adverse effect on our business,
      results of operations and financial condition.
 
                                       17
<PAGE>
WE FACE UNCERTAINTY ABOUT ADDITIONAL FINANCING FOR OUR FUTURE CAPITAL NEEDS.
 
    If we are unable to increase our revenues as anticipated, we will need to
raise additional funds. Although we have historically received financing from
NPD, we will not be able to rely on NPD's assistance in the future. We may need
additional financing sooner if we:
 
    - decide to expand faster than planned;
 
    - develop new or enhanced services or products ahead of schedule;
 
    - need to respond to competitive pressures; or
 
    - need to acquire complementary products, businesses or technologies.
 
    If we raise additional funds through the sale of equity or convertible debt
securities, your percentage ownership will be reduced. In addition, these
transactions may dilute the value of the stock outstanding. We may have to issue
securities that may have rights, preferences and privileges senior to our common
stock. We cannot assure you that we will be able to raise additional funds on
terms favorable to us or at all. If future financing is not available or is not
available on acceptable terms, we may not be able to fund our future needs. This
could have a material adverse effect on our business, results of operations and
financial condition.
 
WE MAY SUFFER AN INTERRUPTION IN OUR BUSINESS.
 
    Our business interruption insurance may not be adequate to compensate us
fully for losses that may occur as a result of an interruption in our business.
Our business, results of operations and financial condition could be materially
and adversely affected if we are unable to conduct our business for an extended
period of time for any reason.
 
OUR PRINCIPAL STOCKHOLDERS, EXECUTIVE OFFICERS AND DIRECTORS HAVE SUBSTANTIAL
  CONTROL OVER OUR AFFAIRS.
 
    Our executive officers and directors and entities affiliated with them will,
in the aggregate, beneficially own approximately 42.3% of our common stock
following this offering or 42.6% if Greylock IX Limited Partnership purchases
its reserved shares in this offering. In particular, NPD, which is controlled by
Tod Johnson, our Chairman and Chief Executive Officer, will own approximately
26.2% of our outstanding common stock. These stockholders acting together will
have the ability to exert substantial influence over all matters requiring
approval by our stockholders. These matters include the election and removal of
directors and any merger, consolidation or sale of all or substantially all of
our assets. In addition, they may dictate the management of our business and
affairs. This concentration of ownership could have the effect of delaying,
deferring or preventing a change in control, or impeding a merger or
consolidation, takeover or other business combination.
 
THERE MAY BE AN ADVERSE EFFECT ON THE MARKET PRICE OF OUR STOCK AS A RESULT OF
SHARES BEING AVAILABLE FOR SALE IN THE FUTURE.
 
    Sales of a substantial amount of common stock in the public market, or the
perception that these sales may occur, could adversely affect the market price
of our common stock prevailing from time to time. This could also impair our
ability to raise additional capital through the sale of our equity securities.
After this offering, we will have 16,727,828 shares of common stock outstanding,
or 16,977,828 shares if the underwriters over-allotment option is exercised in
full. Of these shares, the shares sold in this offering will be freely
tradeable, except for shares purchased by an affiliate of ours, which will be
subject to the limitations of Rule 144 under the Securities Act. The remaining
13,727,828 shares are "restricted shares," and will become eligible for sale in
the public market at various times after 180 days after the date of this
prospectus, subject to the limitations and other conditions of Rule 144 under
the Securities Act.
 
                                       18
<PAGE>
    In addition, after this offering, the holders of 13,480,075 shares of common
stock will have registration rights with respect to these shares. This will
allow these stockholders to sell these shares in the market simultaneously with
any further public offerings by us of our equity securities. See "Shares
Eligible for Future Sale."
 
THERE MAY BE VOLATILITY IN OUR STOCK PRICE.
 
    Prior to this offering, there has been no public market for our common
stock. We cannot predict the extent to which investor interest will lead to the
development of an active and liquid trading market. The initial public offering
price for the shares will be determined by negotiations between us and the
representatives of the underwriters and may not be indicative of the market
price of the common stock that will prevail in the trading market. The market
price of the common stock may decline below the initial public offering price.
The market prices of the securities of Internet-related companies have been
especially volatile. Some companies that have had volatile market prices for
their securities have been subject to securities class action suits filed
against them. If a suit were to be filed against us, regardless of the outcome,
it could result in substantial costs and a diversion of our management's
attention and resources. This could have a material adverse effect on our
business, results of operations and financial condition. See "Underwriting."
 
MANAGEMENT HAS BROAD DISCRETION AS TO THE USE OF PROCEEDS FROM THIS OFFERING.
 
    Our management will have broad discretion with respect to the use of
proceeds from this offering. Most of the proceeds from this offering will be
used for expenses of the business and general working capital. You will be
relying on the judgment of our management about these uses. See "Use of
Proceeds."
 
THE TANGIBLE BOOK VALUE OF THE COMMON STOCK WILL BE SUBSTANTIALLY LOWER THAN THE
  OFFERING PRICE.
 
    The initial public offering price will be substantially higher than the pro
forma tangible book value per share of our outstanding common stock. If you
purchase our common stock in this offering, the shares you buy will experience
an immediate and substantial dilution in tangible book value per share. The
shares of common stock owned by the existing stockholders will receive a
material increase in the tangible book value per share. The dilution to
investors in this offering will be approximately $14.45 per share. As a result,
if we were to distribute our tangible assets to our stockholders immediately
following this offering, purchasers of shares of common stock in this offering
would receive less than the amount paid for such shares. See "Dilution."
 
EFFECTS OF ANTI-TAKEOVER PROVISIONS COULD INHIBIT THE ACQUISITION OF MEDIA
  METRIX.
 
    Some of the provisions of our certificate of incorporation, bylaws and
Delaware law could, together or separately:
 
    - discourage potential acquisitions proposals;
 
    - delay or prevent a change in control; and
 
    - limit the price that investors might be willing to pay in the future for
      shares of our common stock.
 
    In particular, our board of directors may issue up to 5,000,000 shares of
preferred stock with rights and privileges that might be senior to our common
stock, without the consent of the holders of the common stock. Our certificate
of incorporation and bylaws will provide, among other things, that our board of
directors will be divided into three classes which will serve staggered three
year terms, that stockholders may not take actions by written consent and that
special meetings of stockholders may only be called by our board of directors or
our Chairman. We are also subject to Section 203 of the Delaware General
Corporation Law which generally prohibits a Delaware corporation from engaging
in any of a broad range of business combinations with any interested stockholder
for a period of three years following the date on which the stockholder became
an interested stockholder.
 
                                       19
<PAGE>
                                USE OF PROCEEDS
 
    The net proceeds from the sale of the 3,000,000 shares of common stock
offered by us will be approximately $46.4 million, after deducting underwriting
discounts and commissions and other estimated offering expenses. If the
underwriters' over-allotment option is exercised in full, such net proceeds will
be approximately $50.4 million.
 
    We will use at least $5.5 million of the net proceeds from this offering to
fund investments in our planned European joint venture, Media Metrix Europe. We
plan on making additional investments in our international expansion efforts. We
have no present plans or commitments with respect to any such investments.
 
    We will also use approximately $4.8 million of the net proceeds from this
offering to redeem the 41,446 shares of our outstanding redeemable preferred
stock held by NPD. The redeemable preferred stock is redeemable at a price of
$100 per share plus accrued dividends at an annual rate of 7%, compounded
quarterly. At April 30, 1999, principal and accrued dividends equaled
approximately $4.8 million.
 
    The remaining amounts will be used to develop new products and for general
corporate purposes, including working capital. We may also use a portion of the
net proceeds, currently intended for general corporate purposes, to acquire or
to invest in complementary businesses, technologies, products or services. We
have no present plans or commitments and we are not currently engaged in any
negotiations with respect to such transactions. Our management will retain broad
discretion in the allocation of the net proceeds of this offering.
 
    Pending such uses, we intend to invest the net proceeds in short-term,
investment grade, interest-bearing securities.
 
                                DIVIDEND POLICY
 
    We have never declared nor paid any cash dividends on our common stock. We
currently anticipate that we will retain any future earnings for the development
and operations of our business. Accordingly, we do not anticipate paying cash
dividends on our capital stock in the foreseeable future.
 
                                       20
<PAGE>
                                 CAPITALIZATION
 
    The following table sets forth our capitalization as of March 31, 1999 and
as adjusted to reflect our sale of the shares of common stock in this offering
at the initial public offering price of $17.00 per share and the application of
the net proceeds as described under the section "Use of Proceeds." You should
read the following table with "Management's Discussion and Analysis of Financial
Condition and Results of Operations" and the financial statements and notes
included elsewhere in this prospectus.
<TABLE>
<CAPTION>
                                                                       AS OF MARCH 31, 1999
                                                                    --------------------------
<S>                                                                 <C>         <C>
                                                                      ACTUAL     AS ADJUSTED
 
<CAPTION>
                                                                          (IN THOUSANDS)
<S>                                                                 <C>         <C>
Long-term debt, including current portion.........................  $      323    $      323
Redeemable preferred stock, $.01 par value; 41,446 shares
  authorized, issued and outstanding, actual; no shares
  authorized, issued and outstanding, as adjusted.................       4,762            --
Stockholders' equity:
  Preferred stock, $.01 par value, 4,958,554 shares authorized;
    none issued and outstanding, actual; 5,000,000 shares
    authorized and none issued and outstanding, as adjusted.......          --            --
  Common stock, $.01 par value, 60,000,000 shares authorized and
    13,727,828 shares issued and outstanding, actual; 16,727,828
    shares issued and outstanding, as adjusted....................         137           167
  Additional paid-in capital......................................      21,353        67,753
  Accumulated deficit.............................................     (18,560)      (18,560)
  Deferred compensation...........................................      (1,456)       (1,456)
                                                                    ----------  --------------
Total stockholders' equity........................................       1,474        47,904
                                                                    ----------  --------------
    Total capitalization..........................................  $    6,559    $   48,227
                                                                    ----------  --------------
                                                                    ----------  --------------
</TABLE>
 
   The outstanding share information is based on our shares outstanding as of
    March 31, 1999. This information excludes:
 
    - 462,907 shares of common stock subject to options granted under our 1998
      Equity Incentive Plan and outstanding as of March 31, 1999 at a weighted
      average exercise price of $7.47 per share;
 
    - 496,283 shares of common stock subject to options granted under our
      earlier Stock Option Plan and outstanding as of March 31, 1999 at a
      weighted average exercise price of $0.84 per share;
 
    - 854,648 additional shares of common stock reserved for issuance under our
      1998 Equity Incentive Plan; and
 
    - 469,413 shares of common stock reserved for outstanding warrants at a
      weighted average exercise price of $1.87 per share.
 
                                       21
<PAGE>
                                    DILUTION
 
    Our net tangible book value as of March 31, 1999, was approximately $(3.9)
million, or $(0.29) per share of common stock. Net tangible book value per share
is equal to our tangible net assets, less total liabilities, divided by the
number of shares of common stock outstanding as of March 31, 1999. Net tangible
book value dilution per share to new investors represents the difference between
the amount per share paid by purchasers of shares of common stock in this
offering and the net tangible book value per share of common stock immediately
after completion of this offering. After giving effect to the sale of 3,000,000
shares at the initial offering price of $17.00 per share and the application of
the net proceeds from this offering, our net tangible adjusted book value at
March 31, 1999 would have been approximately $42.7 million, or $2.55 per share
of common stock. This amount represents an immediate increase in net tangible
book value of $2.84 per share to existing stockholders and an immediate dilution
in net tangible book value of $14.45 per share to new investors. The following
table illustrates this per share dilution:
 
<TABLE>
<S>                                                                      <C>        <C>
Initial public offering price per share................................             $   17.00
  Net tangible book value per share at March 31, 1999..................  $   (0.29)
  Increase per share attributable to new investors.....................       2.84
                                                                         ---------
Net tangible book value per share after the offering...................                  2.55
                                                                                    ---------
Dilution per share to new investors....................................             $   14.45
                                                                                    ---------
                                                                                    ---------
</TABLE>
 
    The following table summarizes, as of March 31, 1999, the total number of
shares of common stock purchased from us, the total consideration paid to us,
and the average price per share paid by our existing stockholders and by new
investors purchasing shares from us in the offering, before deducting
underwriting discounts and commissions and the estimated offering expenses
payable by us:
 
<TABLE>
<CAPTION>
                                                             SHARES PURCHASED          TOTAL CONSIDERATION        AVERAGE
                                                         -------------------------  --------------------------   PRICE PER
                                                            NUMBER       PERCENT       AMOUNT        PERCENT       SHARE
<S>                                                      <C>           <C>          <C>            <C>          <C>
Existing stockholders(1)...............................    13,727,828        82.1%  $  19,915,994        28.1%   $    1.45
New investors..........................................     3,000,000        17.9      51,000,000        71.9        17.00
                                                         ------------       -----   -------------       -----
    Total..............................................    16,727,828       100.0%  $  70,915,994       100.0%
                                                         ------------       -----   -------------       -----
                                                         ------------       -----   -------------       -----
</TABLE>
 
- -----------------------
 
(1) Includes $10,500,000, representing the value of the 3,890,825 shares of
    common stock issued in connection with our merger with RelevantKnowledge.
 
    If the underwriters exercise their over-allotment option in full, the number
of shares of common stock held by existing stockholders will be reduced to
13,527,828 or 79.7% of the total number of shares of common stock to be
outstanding after this offering. In addition, the number of shares of common
stock held by the new investors will be increased to 3,450,000, or 20.3% of the
total number of shares of common stock to be outstanding immediately after this
offering.
 
    The outstanding share information is based on our shares outstanding as of
March 31, 1999. This information excludes:
 
    - 462,907 shares of common stock subject to options granted under our 1998
      Equity Incentive Plan and outstanding as of March 31, 1999 at a weighted
      average exercise price of $7.47 per share;
 
    - 496,283 shares of common stock subject to options granted under our
      earlier Stock Option Plan and outstanding as of March 31, 1999 at a
      weighted average exercise price of $0.84 per share;
 
    - 854,648 additional shares of common stock reserved for issuance under our
      1998 Equity Incentive Plan; and
 
    - 469,413 shares of common stock reserved for outstanding warrants at a
      weighted average exercise price of $1.87 per share.
 
                                       22
<PAGE>
                            SELECTED FINANCIAL DATA
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)
 
    The selected financial data set forth below as of December 31, 1996, 1997
and 1998 have been derived from our financial statements, which have been
audited by Ernst & Young LLP, independent auditors, whose report for the three
years ended December 31, 1998 is included elsewhere in this prospectus. The
statement of operations for the period ended December 31, 1995 and for the three
months ended March 31, 1998 and 1999 and the balance sheet as of March 31, 1999
are unaudited and, in our opinion, include all adjustments, consisting of only
normal recurring adjustments, necessary for a fair presentation of the
information. The financial statements for the period from inception to December
31, 1995 are based on operations of PC Meter, our predecessor, while it was
still a division of NPD. The financial statements for the year ended December
31, 1996 are those of PC Meter and include three months of operations during
which PC Meter was a division of NPD. The financial statements for the year
ended December 31, 1998 include the results of operations of RelevantKnowledge
from the date of the merger on November 5, 1998. The pro froma financial
statements for the year ended December 31, 1998 give effect to the
RelevantKnowledge merger as if it had taken place on January 1, 1998. The
results of operations for the three months ended March 31, 1999 are not
necessarily indicative of results to be expected for any future period. You
should read the selected financial data set forth below with the financial
statements and related notes and with "Management's Discussion and Analysis of
Financial Condition and Results of Operations," which are included elsewhere in
this prospectus.
 
<TABLE>
<CAPTION>
                                       PERIOD FROM                                                           THREE MONTHS ENDED
                                        INCEPTION                  YEAR ENDED                  PRO FORMA
                                         THROUGH                  DECEMBER 31,                YEAR ENDED         MARCH 31,
                                      DECEMBER 31,    -------------------------------------  DECEMBER 31,   --------------------
                                          1995           1996         1997         1998          1998         1998       1999
<S>                                  <C>              <C>          <C>          <C>          <C>            <C>        <C>
STATEMENT OF OPERATIONS DATA:
  Revenues.........................     $      --      $   1,033    $   3,188    $   6,331     $   8,145    $   1,160  $   3,178
  Costs of revenues................           140          1,744        3,463        4,121         7,000          800      1,720
                                           ------     -----------  -----------  -----------  -------------  ---------  ---------
  Gross profit (loss)..............          (140)          (711)        (275)       2,210         1,145          360      1,458
  Operating expenses:
    Research and development.......            86            588          866        1,382         2,162          248        681
    Sales and marketing............            45            929        2,022        2,888         4,512          575      1,334
    General and administrative.....           101          1,148        1,516        3,084         6,057          434      1,157
    Amortization of intangibles....            --             --           --          479         2,872           --        749
    Acquired in-process research
      and development..............            --             --           --        1,600         1,600           --         --
                                           ------     -----------  -----------  -----------  -------------  ---------  ---------
      Total operating expenses.....           232          2,665        4,404        9,433        17,203        1,257      3,921
                                           ------     -----------  -----------  -----------  -------------  ---------  ---------
  Loss from operations.............          (372)        (3,376)      (4,679)      (7,223)      (16,058)        (897)    (2,463)
  Interest income, net of interest
    expense........................            --             --           95           65           161           45         79
                                           ------     -----------  -----------  -----------  -------------  ---------  ---------
  Net loss.........................          (372)        (3,376)      (4,584)      (7,158)      (15,897)        (852)    (2,384)
  Preferred stock dividends........            --             --         (290)        (314)         (314)         (77)       (82)
                                           ------     -----------  -----------  -----------  -------------  ---------  ---------
  Net loss available to common
    stockholders...................     $    (372)     $  (3,376)   $  (4,874)   $  (7,472)    $ (16,211)   $    (929) $  (2,466)
                                           ------     -----------  -----------  -----------  -------------  ---------  ---------
                                           ------     -----------  -----------  -----------  -------------  ---------  ---------
  Basic and diluted net loss per
    common share applicable to
    common stockholders............     $   (0.06)     $   (0.52)   $   (0.75)   $   (0.98)    $   (1.49)   $   (0.14) $   (0.19)
                                           ------     -----------  -----------  -----------  -------------  ---------  ---------
                                           ------     -----------  -----------  -----------  -------------  ---------  ---------
  Shares used in calculating basic
    and diluted net loss per common
    share applicable to common
    stockholders...................         6,523          6,523        6,523        7,619        10,861        6,523     13,296
</TABLE>
 
<TABLE>
<CAPTION>
                                                                           AS OF DECEMBER 31,
                                                                     -------------------------------  AS OF MARCH 31,
                                                                       1996       1997       1998          1999
<S>                                                                  <C>        <C>        <C>        <C>
BALANCE SHEET DATA:
Cash and cash equivalents..........................................  $     583  $   1,869  $   8,012     $   2,385
Working capital (deficit)..........................................     (2,478)       (47)     1,057           312
Total assets.......................................................      1,213      2,787     16,060        11,240
Due to NPD.........................................................      2,782      1,284      4,706         1,339
Preferred stocks...................................................         --      8,366      4,680         4,762
Total stockholders' equity (deficit)...............................     (2,478)    (8,274)     2,622         1,474
</TABLE>
 
                                       23
<PAGE>
                    MANAGEMENT'S DISCUSSION AND ANALYSIS OF
                 FINANCIAL CONDITION AND RESULTS OF OPERATIONS
 
    YOU SHOULD READ THE FOLLOWING DISCUSSION OF OUR FINANCIAL CONDITION AND
RESULTS OF OPERATIONS WITH THE FINANCIAL STATEMENTS AND THE NOTES TO THE
FINANCIAL STATEMENTS INCLUDED ELSEWHERE IN THIS PROSPECTUS. THIS DISCUSSION
CONTAINS FORWARD-LOOKING STATEMENTS BASED ON OUR CURRENT EXPECTATIONS,
ASSUMPTIONS, ESTIMATES AND PROJECTIONS. THESE FORWARD-LOOKING STATEMENTS INVOLVE
RISKS AND UNCERTAINTIES. OUR ACTUAL RESULTS COULD DIFFER MATERIALLY FROM THOSE
ANTICIPATED IN THESE FORWARD-LOOKING STATEMENTS AS A RESULT OF CERTAIN FACTORS,
AS MORE FULLY DESCRIBED IN THE "RISK FACTORS" SECTION AND ELSEWHERE IN THIS
PROSPECTUS. WE UNDERTAKE NO OBLIGATION TO UPDATE PUBLICLY ANY FORWARD-LOOKING
STATEMENTS FOR ANY REASON, EVEN IF NEW INFORMATION BECOMES AVAILABLE OR OTHER
EVENTS OCCUR IN THE FUTURE.
 
OVERVIEW
 
    We provide Internet audience measurement products and services to leading
Internet advertisers and advertising agencies, Internet properties, technology
companies and financial institutions. We have been at the forefront of the
development and coordination of technology and standards needed to facilitate
advertising and transactions between companies doing business over the Internet.
The quality and depth of our customer base and our customer renewal rate of over
95% reflect our position as a widely accepted Internet audience measurement
service.
 
    Our business was originally conducted as a division within NPD, a leading
marketing research firm. Prior to March 1996, we were engaged primarily in
product research and development. In March 1996, PC Meter, L.P., was formed to
further commercialize our Internet audience measurement business in an entity
separate from NPD, although NPD continued to provide PC Meter with
administrative and support services and technology licenses. By July 1996, we
increased the size of our panel to over 10,000 individuals and significantly
increased our product offerings. In April 1997, PC Meter was merged into Media
Metrix and we raised approximately $4.0 million in a private placement to fund
the expansion of our business. The assets and liabilities and related revenues
and expenses of PC Meter have been reflected in our financial statements at
their historical book values. See "Certain Transactions--Formation by NPD,"
financial statements and related notes thereto.
 
    In November 1998, we merged with RelevantKnowledge, our leading competitor.
After giving effect to the merger, the former stockholders of RelevantKnowledge
were issued 3,890,825 shares of Media Metrix common stock. See Note 4 of notes
to our financial statements. Following the merger, we increased our panel size
and began to integrate the best technological features from each company into
our systems and processes. Due to the combination, in the fourth quarter of 1998
we had considerable expenses due to costs incurred by operating two distinct
panels, production systems and administrative infrastructures. We anticipate
that these costs will decrease as we more fully integrate the businesses and
operations of the two companies. In connection with the merger, we acquired $6.4
million of intangibles, which will be amortized over a period varying from one
to three years.
 
    Our revenues are derived from our measurement products and services. Our
product offerings include both syndicated products and customized products. We
sell our syndicated products on an annual subscription basis. We typically bill
our syndicated clients, in advance, for the next three months of products. Since
1997, syndicated products have accounted for approximately 90% of our revenues,
while customized products and services have accounted for approximately 10%. Our
combined customer base increased from approximately 100 customers at the end of
1997 to more than 350 as of March 31, 1999. Of the 75 customers subscribing
under annual contracts for our syndicated products and services at the end of
1997, over 95% remained customers at the end of 1998. With this high customer
retention rate, we have a growing base of recurring revenues from our syndicated
products and services.
 
                                       24
<PAGE>
    We recognize revenues for the syndicated products and services over the term
of the related contract as services are provided. Revenues for customized
products and services are recognized in the period in which the product or
service is delivered.
 
    Our business model is based on creating multiple products and services from
our core panel-based market research, technologies and databases. The core panel
of 40,000 individuals under continuous measurement has been established over the
past three years. We recruit individuals to become members of our panel through
random direct mail and telephone solicitations. We incur costs in connection
with recruiting and retaining members of our panel. These costs are expensed in
the year incurred. We plan to introduce a new version of our patented metering
technology in 1999, which is expected to reduce the use of mail in connection
with the panel and provide cost savings. Our rate of expense growth, other than
panel and production, is primarily driven by increases in headcount and sales
and marketing expenditures.
 
    We have incurred significant losses from operations since our inception. We
incurred losses from operations of $3.4 million in 1996, $4.7 million in 1997,
$7.2 million in 1998 and $2.5 million in the three months ended March 31, 1999.
If the merger with RelevantKnowledge had taken place on January 1, 1998, our pro
forma loss from operations for 1998 would have been $16.1 million. This pro
forma loss from operations includes a full year of amortization of $2.9 million
of intangibles and a non-cash expense recorded for the issuance of warrants of
$971,000. As of March 31, 1999, we had an accumulated deficit of $18.6 million.
As of December 31, 1998, we had an outstanding payable to NPD for $4.7 million
under the management services agreement, $4.1 million of which was paid in
January 1999. As of March 31, 1999, we had an outstanding payable to NPD for
$1.3 million. Charges from NPD are expected to decrease in 1999 as we take on
the direct management of our own payroll and computer systems.
 
    We expect that we will incur significant expenses in the future associated
with our planned international expansion. In particular, we plan on hiring
senior personnel to manage the anticipated international operations and on
entering into joint ventures with local partners. This will probably involve the
recruitment of a panel and the expenditure of significant funds. In addition, we
intend to invest heavily in further development and improvement of our
technologies and development of additional products and services.
 
RESULTS OF OPERATIONS
 
    The following table sets forth our results of operations expressed as a
percentage of revenues:
 
<TABLE>
<CAPTION>
                                                                                                 THREE MONTHS ENDED
                                                                   YEAR ENDED DECEMBER 31,           MARCH 31,
                                                               -------------------------------  --------------------
<S>                                                            <C>        <C>        <C>        <C>        <C>
                                                                 1996       1997       1998       1998       1999
Revenues.....................................................      100.0%     100.0%     100.0%     100.0%     100.0%
Costs of revenues............................................      168.9      108.6       65.1       69.0       54.1
                                                               ---------  ---------  ---------  ---------  ---------
Gross profit (loss)..........................................      (68.9)      (8.6)      34.9       31.0       45.9
Operating expenses:
  Research and development...................................       56.9       27.2       21.8       21.4       21.4
  Sales and marketing........................................       90.0       63.4       45.6       49.6       42.0
  General and administrative.................................      111.1       47.6       48.7       37.4       36.4
  Amortization of intangibles................................         --         --        7.6         --       23.6
  Acquired in-process research and development...............         --         --       25.3         --         --
                                                               ---------  ---------  ---------  ---------  ---------
Total operating expenses.....................................      258.0      138.2      149.0      108.4      123.4
                                                               ---------  ---------  ---------  ---------  ---------
Loss from operations.........................................     (326.9)    (146.8)    (114.1)     (77.4)     (77.5)
Interest income, net.........................................         --        3.0        1.0        3.9        2.5
                                                               ---------  ---------  ---------  ---------  ---------
Net loss.....................................................     (326.9)%    (143.8)%    (113.1)%     (73.5)%     (75.0)%
                                                               ---------  ---------  ---------  ---------  ---------
                                                               ---------  ---------  ---------  ---------  ---------
</TABLE>
 
                                       25
<PAGE>
THREE MONTHS ENDED MARCH 31, 1998 COMPARED TO THREE MONTHS ENDED MARCH 31, 1999
 
    REVENUES.  Revenues increased 174.0% from $1.2 million for the three months
ended March 31, 1998 to $3.2 million for the three months ended March 31, 1999.
Sales of syndicated audience measurement products and services accounted for
approximately 90% of revenues for each of the three months ended March 31, 1998
and 1999. Sales of customized products and services accounted for the remaining
revenues. The increase in revenues was due primarily to a substantial increase
in the number of our customers, including customers acquired in connection with
the RelevantKnowledge merger, and an increase in the amount of products and
services sold to our customers. No single customer accounted for more than 10%
of revenues during either of the three months ended March 31, 1998 and 1999.
 
    COSTS OF REVENUES.  Costs of revenues consist primarily of costs associated
with the recruitment and maintenance of the panel, data collection and
production costs. Panel and data collection costs include costs associated with
mailing and printing, incentives, help desk and associated personnel. Production
costs include computer usage charges, printing, report distribution costs and
personnel costs. Gross profit was $360,000 for the three months ended March 31,
1998, or 31.0% of revenues. Gross profit was $1.5 million for the three months
ended March 31, 1999, or 45.9% of revenues. The increase in gross profit as a
percentage of revenues for the three months ended March 31, 1999 over the prior
period was due to an increase in revenues, without a commensurate increase in
costs. The increase in gross profit was partially offset by the costs associated
with operating a substantially larger panel following the RelevantKnowedge
merger.
 
    RESEARCH AND DEVELOPMENT.  Research and development costs consist primarily
of personnel and other related costs attributable to the development of new
products and services. All research and development costs have been expensed as
incurred. Research and development costs were $248,000 for the three months
ended March 31, 1998, or 21.4% of revenues. Research and development costs were
$681,000 for the three months ended March 31, 1999, or 21.4% of revenues. The
increase in absolute dollars was due primarily to increases in research and
development personnel, including the addition of personnel in connection with
the RelevantKnowedge merger.
 
    SALES AND MARKETING.  Sales and marketing costs consist of personnel,
commissions, travel and entertainment expenses, public relations costs, trade
show expenses, seminars and marketing materials. Sales and marketing costs were
$575,000 for the three months ended March 31, 1998, or 49.6% of revenues. Sales
and marketing costs were $1.3 million for the three months ended March 31, 1999,
or 42.0% of revenues. The increase in absolute dollars was due primarily to the
increase in sales and marketing personnel, including the addition of personnel
in connection with the RelevantKnowedge merger, and additional marketing costs.
The decrease in sales and marketing costs as a percentage of revenues was due
primarily to revenues increasing at a greater rate.
 
    GENERAL AND ADMINISTRATIVE.  General and administrative costs consist
primarily of personnel, lease payments for our facilities, telephone and
utilities and professional services fees. General and administrative costs were
$434,000 for the three months ended March 31, 1998, or 37.4% of revenues.
General and administrative costs were $1.2 million for the three months ended
March 31, 1999, or 36.4% of revenues. The increase in absolute dollars was due
to the expenses associated with increased personnel and expansion of our office
facilities, including the addition of personnel and office facilities in
connection with the RelevantKnowedge merger, and a non-cash compensation expense
recorded in connection with stock options. The decrease in general and
administrative costs as a percentage of revenues was due primarily to revenues
increasing at a greater rate. We anticipate that our general and administrative
costs will increase as a result of expenses associated with becoming a public
company.
 
    AMORTIZATION OF INTANGIBLES.  Amortization charges of $749,000 for the three
months ended March 31, 1999 represent the amortization of RelevantKnowledge's
panel, which is being amortized
 
                                       26
<PAGE>
over 12 months, and amortization of other intangibles acquired in our merger
with RelevantKnowedge, which are being amortized over three years.
 
    LOSS FROM OPERATIONS.  Our loss from operations was $897,000 for the three
months ended March 31, 1998, or (77.4)% of revenues. Loss from operations was
$2.5 million for the three months ended March 31, 1999, or (77.5)% of revenues.
Loss from operations was higher in the three months ended March 31, 1999 due to
the continued expansion of our business, the merger with RelevantKnowedge and
amortization of intangibles. The decrease in loss from operations as a
percentage of revenues was due to an increase in revenues relative to the
increases in costs of revenues and operating costs.
 
YEAR ENDED DECEMBER 31, 1997 COMPARED TO YEAR ENDED DECEMBER 31, 1998
 
    REVENUES.  Revenues increased 98.6% from $3.2 million for the year ended
December 31, 1997 to $6.3 million for the year ended December 31, 1998. Sales of
syndicated audience measurement products and services accounted for
approximately 90% of revenues for the years ended December 31, 1997 and 1998,
respectively. Sales of customized products and services accounted for the
remaining revenues. The increase in revenues was due primarily to a substantial
increase in the number of our customers and an increase in the amount of
products and services sold to our customers, and, to a lesser extent, the
revenues associated with RelevantKnowledge's business for the period from
November 5, 1998 to the end of the year. No single customer accounted for more
than 10% of revenues during the year ended December 31, 1998. One customer
accounted for approximately 19% of revenues for the year ended December 31,
1997.
 
    COSTS OF REVENUES.  Gross loss was $275,000 for the year ended December 31,
1997, or (8.6)% of revenues. Gross profit was $2.2 million for the year ended
December 31, 1998, or 34.9% of revenues. The increase in gross profit for the
year ended December 31, 1998 over the prior period was due to an increase in
sales, including sales attributable to RelevantKnowledge's business for the
period from November 5, 1998 to the end of the year, without a commensurate
increase in costs. The increase in gross profit was partially offset by the
costs associated with operating two panels following the RelevantKnowledge
merger.
 
    RESEARCH AND DEVELOPMENT.  Research and development costs were $866,000 for
the year ended December 31, 1997, or 27.2% of revenues. Research and development
costs were $1.4 million for the year ended December 31, 1998, or 21.8% of
revenues. The increase in absolute dollars was due primarily to increases in
research and development personnel, including the addition of personnel in
connection with the RelevantKnowledge merger. The decrease in research and
development costs as a percentage of revenues was due to revenues increasing at
a greater rate.
 
    SALES AND MARKETING.  Sales and marketing costs were $2.0 million for the
year ended December 31, 1997, or 63.4% of revenues. Sales and marketing costs
were $2.9 million for the year ended December 31, 1998, or 45.6% of revenues.
The increase in absolute dollars was due primarily to the increase in sales and
marketing personnel, including the addition of personnel in connection with the
RelevantKnowledge merger. The decrease in sales and marketing costs as a
percentage of revenues was due primarily to revenues increasing at a greater
rate.
 
    GENERAL AND ADMINISTRATIVE.  General and administrative costs were $1.5
million for the year ended December 31, 1997, or 47.6% of revenues. General and
administrative costs were $3.1 million for the year ended December 31, 1998, or
48.7% of revenues. The increase in absolute dollars was due to the expenses
associated with increased personnel, expansion of our office facilities,
expenses incurred after the merger with RelevantKnowledge and a non-cash
compensation expense recorded in connection with stock options. The decrease in
general and administrative costs as a percentage of revenues was due primarily
to revenues increasing at a greater rate.
 
                                       27
<PAGE>
    AMORTIZATION OF INTANGIBLES.  Amortization charges of $479,000 represent two
months of the amortization of RelevantKnowledge's panel, which is being
amortized over 12 months and other intangibles acquired in our merger with
RelevantKnowledge which are being amortized over three years.
 
    ACQUIRED IN-PROCESS RESEARCH AND DEVELOPMENT.  In connection with our merger
with RelevantKnowledge, we expensed $1.6 million of acquired in-process research
and development for the year ended December 31, 1998. Acquired in-process
research and development represents the value attributed to three technologies
in development at the time of the merger.
 
    LOSS FROM OPERATIONS.  Our loss from operations was $4.7 million for the
year ended December 31, 1997, or (146.8)% of revenues. Loss from operations was
$7.2 million for the year ended December 31, 1998, or (114.1)% of revenues. Loss
from operations was higher in 1998 due to the continued expansion of our
business, the inclusion of two months of RelevantKnowledge losses and
amortization of acquired intangibles. Loss from operations in 1998 included a
$1.6 million write-off of acquired in-process research and development. The
decrease in loss from operations as a percentage of revenues was due primarily
to an increase in sales relative to the increases in costs of revenues and
operating costs.
 
YEAR ENDED DECEMBER 31, 1996 COMPARED TO YEAR ENDED DECEMBER 31, 1997
 
    REVENUES.  Revenues increased 208.7% from $1.0 million for the year ended
December 31, 1996 to $3.2 million for the year ended December 31, 1997. Sales of
syndicated audience measurement products and services accounted for
approximately 90% of revenues for the years ended December 31, 1996 and 1997.
Sales of customized products and services accounted for most of the remaining
revenues. The increase in revenues was due primarily to a substantial increase
in the number of our customers and an increase in the amount of services sold to
our customers. One customer accounted for approximately 19% of revenues for the
year ended December 31, 1997. No single customer accounted for more than 10% of
revenues during the year ended December 31, 1996.
 
    COSTS OF REVENUES.  Gross loss was $711,000 for the year ended December 31,
1996, or (68.9)% of revenues. Gross loss was $275,000 for the year ended
December 31, 1997, or (8.6)% of revenues. Costs of revenues increased
substantially in 1997 due to costs associated with panel expansion. The decrease
in the costs of revenues as a percentage of revenues was due primarily to
revenues increasing at a greater rate.
 
    RESEARCH AND DEVELOPMENT.  Research and development costs were $588,000 for
the year ended December 31, 1996, or 56.9% of revenues. Research and development
costs were $866,000 for the year ended December 31, 1997, or 27.2% of revenues.
The decrease in research and development costs as a percentage of revenues was
due to revenues increasing at a greater rate.
 
    SALES AND MARKETING.  Sales and marketing costs were $929,000 for the year
ended December 31, 1996, or 90.0% of revenues. Sales and marketing costs were
$2.0 million for the year ended December 31, 1997, or 63.4% of revenues. The
increase in absolute dollars was due primarily to the increase in sales and
marketing personnel and expansion of marketing efforts. The decrease in sales
and marketing costs as a percentage of revenues was due primarily to revenues
increasing at a greater rate.
 
    GENERAL AND ADMINISTRATIVE.  General and administrative costs were $1.1
million for the year ended December 31, 1996, or 111.1% of revenues. General and
administrative costs were $1.5 million for the year ended December 31, 1997, or
47.6% of revenues. The increase in absolute dollars was due primarily to the
expenses associated with increased personnel and associated expansion of our
infrastructure. The decrease in general and administrative costs as a percentage
of revenues was due primarily to revenues increasing at a greater rate.
 
                                       28
<PAGE>
    LOSS FROM OPERATIONS.  Our loss from operations was $3.4 million for the
year ended December 31, 1996, or (326.9)% of revenues. Loss from operations was
$4.7 million for the year ended December 31, 1997, or (146.8)% of revenues. The
decrease in the loss from operations as a percentage of revenues was due
primarily to the large increase in revenues relative to the increases in costs
of revenues and operating costs.
 
QUARTERLY RESULTS OF OPERATIONS
 
    The following is a table of unaudited quarterly statement of operations data
for each of the periods indicated. This information is unaudited, but in our
opinion, has been prepared substantially on the same basis as our audited
financial statements, which are included elsewhere in this prospectus. All
necessary adjustments, consisting only of normal recurring adjustments, have
been included in these amounts to present fairly the unaudited quarterly results
of operations. You should read these quarterly data in conjunction with our
audited financial statements. You should not view the results of operations for
any period as an indication of the results of operations for any future period.
<TABLE>
<CAPTION>
                                                                                 QUARTER ENDED
                                                          -----------------------------------------------------------
<S>                                                       <C>          <C>          <C>          <C>        <C>
                                                           MAR. 31,     JUNE 30,     SEPT. 30,   DEC. 31,   MAR. 31,
                                                             1998         1998         1998        1998       1999
 
<CAPTION>
                                                                                (IN THOUSANDS)
<S>                                                       <C>          <C>          <C>          <C>        <C>
Revenues................................................   $   1,160    $   1,345    $   1,493   $   2,333  $   3,178
Costs of revenues.......................................         800          801          885       1,635      1,720
                                                          -----------  -----------  -----------  ---------  ---------
Gross profit............................................         360          544          608         698      1,458
Operating expenses:
  Research and development..............................         248          260          274         600        681
  Sales and marketing...................................         575          711          664         938      1,334
  General and administrative............................         434          412          633       1,605      1,157
  Amortization of intangibles...........................      --           --           --             479        749
  Acquired in-process research and development..........      --           --           --           1,600     --
                                                          -----------  -----------  -----------  ---------  ---------
Total operating expenses................................       1,257        1,383        1,571       5,222      3,921
                                                          -----------  -----------  -----------  ---------  ---------
Loss from operations....................................        (897)        (839)        (963)     (4,524)    (2,463)
Interest income, net of interest expense................          45            4            7           9         79
                                                          -----------  -----------  -----------  ---------  ---------
Net loss................................................   $    (852)   $    (835)   $    (956)  $  (4,515) $  (2,384)
                                                          -----------  -----------  -----------  ---------  ---------
                                                          -----------  -----------  -----------  ---------  ---------
</TABLE>
 
<TABLE>
<CAPTION>
                                                                                 QUARTER ENDED
                                                          -----------------------------------------------------------
<S>                                                       <C>          <C>          <C>          <C>        <C>
                                                           MAR. 31,     JUNE 30,     SEPT. 30,   DEC. 31,   MAR. 31,
                                                             1998         1998         1998        1998       1999
Revenues................................................       100.0%       100.0%       100.0%      100.0%     100.0%
Costs of revenues.......................................        69.0         59.6         59.3        70.1       54.1
                                                          -----------  -----------  -----------  ---------  ---------
Gross profit............................................        31.0         40.4         40.7        29.9       45.9
Operating expenses:
  Research and development..............................        21.4         19.3         18.3        25.7       21.4
  Sales and marketing...................................        49.6         52.9         44.5        40.2       42.0
  General and administrative............................        37.4         30.6         42.4        68.8       36.4
  Amortization of intangibles...........................      --           --           --            20.5       23.6
  Acquired in-process research and development..........      --           --           --            68.6     --
                                                          -----------  -----------  -----------  ---------  ---------
Total operating expenses................................       108.4        102.8        105.2       223.8      123.4
                                                          -----------  -----------  -----------  ---------  ---------
Loss from operations....................................       (77.4)       (62.4)       (64.5)     (193.9)     (77.5)
Interest income, net of interest expense................         3.9          0.3          0.5         0.4        2.5
                                                          -----------  -----------  -----------  ---------  ---------
Net loss................................................       (73.5)%      (62.1)%      (64.0)%    (193.5)%     (75.0)%
                                                          -----------  -----------  -----------  ---------  ---------
                                                          -----------  -----------  -----------  ---------  ---------
</TABLE>
 
                                       29
<PAGE>
    Our revenues have increased in all periods presented as a result of the
continuous expansion of our customer base, the sale of additional products and
services to our existing customers and the release of new products and services.
Results for the three months ended December 31, 1998 and March 31, 1999 reflect
the merger with RelevantKnowledge and, therefore, are not comparable to prior
periods. The results for those two periods include amortization of intangibles
and the write-off of acquired in-process research and development in association
with the merger, a non-cash compensation expense recorded in connection with
stock options and expenses due to costs incurred by operating two distinct
panels, production systems and infrastructures.
 
    Our results of operations may fluctuate significantly in the future as a
result of a variety of factors, many of which are beyond our control. See "Risk
Factors--Our Operating Results May Fluctuate From Quarter to Quarter."
 
LIQUIDITY AND CAPITAL RESOURCES
 
    Since our inception, we have financed our operations primarily through an
initial investment and loan by NPD, the private placement of equity securities,
RelevantKnowledge's cash on hand at the time of the merger and cash from
operations. In April 1997, we completed a $4.0 million private placement of our
equity securities. On November 4, 1998, some of our warrant holders exercised
warrants and acquired common stock for an aggregate purchase price of $1.5
million. On January 4, 1999, we issued to an existing stockholder common stock
for an aggregate of $2.0 million, which had been received by December 31, 1998.
 
    Net cash used in operating activities was $342,000 for the year ended
December 31, 1996, $4.8 million for the year ended December 31, 1997, $411,000
for the year ended December 31, 1998 and $6.7 million for the three months ended
March 31, 1999. For each of these periods, net cash used in operating activities
was substantially impacted by the amount owed to NPD. In the year ended December
31, 1998, the amounts owed to NPD increased by $3.4 million.
 
    Net cash provided by (used in) investing activities was zero for the year
ended December 31, 1996, $(135,000) for the year ended December 31, 1997, $3.1
million for the year ended December 31, 1998 and $(52,000) for the three months
ended March 31, 1999. Cash provided by investing activities for the year ended
December 31, 1998 resulted primarily from the acquisition of $3.2 million of
cash in the RelevantKnowledge transaction.
 
    Net cash provided by financing activities was $925,000 for the year ended
December 31, 1996, $6.2 million for the year ended December 31, 1997, $3.5
million for the year ended December 31, 1998 and $1.1 million for the three
months ended March 31, 1999. Cash provided by financing activities for the year
ended December 31, 1998 resulted from the $1.5 million proceeds from the
exercise of warrants and the receipt of $2.0 million on December 31, 1998
relating to the sale of common stock in January 1999. Cash provided by financing
activities for the three months ended March 31, 1999 was primarily due to the
proceeds received from the exercise of warrants and stock options.
 
    As of March 31, 1999, we had $2.4 million of cash and cash equivalents. As
of March 31, 1999, our principal commitments consisted of accrued obligations
under our agreements with NPD in the amount of $1.3 million. In addition, as of
March 31, 1999, our redeemable preferred stock had an aggregate liquidation
value of $4.8 million. All of our redeemable preferred stock is held by NPD. We
intend to use a portion of the net proceeds from this offering to redeem all of
the outstanding redeemable preferred stock. In addition, we expect to invest at
least $5.5 million over the next several years in our European joint venture,
Media Metrix Europe.
 
    Although we have no material commitments for capital expenditures,
management anticipates that we will experience an increase in our capital
expenditures and lease commitments consistent with our
 
                                       30
<PAGE>
anticipated growth in operations, infrastructure and personnel, including in
connection with the anticipated separation of our systems from those of NPD. We
currently anticipate that we will continue to experience growth in our operating
expenses for the foreseeable future and that operating expenses will be a
material use of our cash resources. Although we expect to use net cash in our
business for the forseeable future, we believe that the net proceeds of this
offering, together with our existing cash and cash equivalents and short-term
investments, will be sufficient to meet our anticipated cash needs for working
capital and capital expenditures for at least the next 18 months.
 
YEAR 2000 COMPLIANCE
 
    Many currently installed computer systems and software products are coded to
accept only two-digit entries in the date code field and cannot reliably
distinguish dates beginning on January 1, 2000 from dates prior to the year
2000. Many companies' software and computer systems may need to be upgraded or
replaced in order to correctly process dates beginning in 2000.
 
    STATE OF READINESS
 
    We rely on NPD's computer and communications networks for collecting and
processing much of our data. NPD has advised us that it has substantially
completed a comprehensive review of its products, information systems and
critical suppliers for year 2000 compliance and has reported that its computer
and communications networks are year 2000 compliant.
 
    We reviewed our meter, as well as our internal programs, and preliminarily
determined that there are no significant year 2000 issues within our meter or
our systems or services. We corrected deficiencies which were identified in the
course of our preliminary review of our systems and are currently conducting a
test of the updated software, including software in which deficiencies had been
detected and corrected. We expect that this test will be completed by the end of
April 1999. The results of tests conducted to date show no significant year 2000
issues. We are currently installing new billing, accounting and administrative
systems which are scheduled to be fully operational during 1999 and which have
been represented will be fully year 2000 compliant when fully operational.
 
    Our assessment plan consists of:
 
    - quality assurance testing of our proprietary software, including our
      metering technology;
 
    - contacting third-party vendors and licensors of material hardware,
      software and services that are both directly and indirectly related to the
      collection and processing of the data received from panelists;
 
    - contacting vendors of material non-IT systems;
 
    - assessment of repair or replacement requirements;
 
    - repair or replacement;
 
    - implementation; and
 
    - creation of contingency plans in the event of year 2000 failures.
 
    COSTS
 
    To date, we have not incurred any material expenditures in connection with
identifying or evaluating year 2000 compliance issues. Most of our expenses have
related to, and are expected to continue to relate to, the operating costs
associated with time spent by employees in the evaluation process and year 2000
compliance matters generally. At this time, we do not anticipate that we will
incur significant operating expenses or be required to invest heavily in
computer systems improvements to be year 2000 compliant. However, significant
uncertainty exists concerning the potential costs and effects associated
 
                                       31
<PAGE>
with year 2000 compliance. If expenses relating to year 2000 compliance are
higher than anticipated, it could have a material adverse effect on our
business, results of operations and financial condition.
 
    RISKS
 
    We are not currently aware of any year 2000 compliance problems relating to
our meter or our data collection and retrieval systems that would have a
material adverse effect on our business, results of operations and financial
condition, other than those that are currently being corrected. However, we
cannot assure you that we will not discover year 2000 compliance problems in the
meter or the data retrieval and collection systems that will require substantial
expenditures to correct. In addition, there can be no assurance that third-party
software, hardware or services incorporated into our systems will not need to be
revised or replaced, all of which could be time consuming and expensive. Our
failure to fix the meter or to fix or replace third-party software, hardware or
services on a timely basis could result in lost revenues, increased operating
costs, the loss of customers and other business interruptions, any of which
could have a material adverse effect on our business, results of operations and
financial condition. Moreover, the failure to adequately address year 2000
compliance issues in our meter and our operating systems could result in claims
of mismanagement, misrepresentation or breach of contract and related
litigation, which could be costly and time-consuming to defend.
 
    In addition, we can not assure you that governmental agencies, utility
companies, Internet access companies, third-party service providers and others
outside of our control will be year 2000 compliant. The failure by such entities
to be year 2000 compliant could result in a systemic failure beyond our control,
such as a prolonged Internet, telecommunications or electrical failure, which
could also prevent us from receiving data from our panelists, processing the
data and providing reports to our clients, which would have a material adverse
effect on our business, results of operations and financial condition.
 
    WORST CASE SCENARIO
 
    We believe that our worst case scenario would be a complete failure of the
metering software installed on our panelists' computers due to year 2000
complications. This would lead to a loss of data for the time period during
which the failure is not remedied. Lack of data could prevent us from issuing
our reports for the period during which the failure is not remedied. We will
continue to monitor this and any other potential problem areas.
 
    CONTINGENCY PLAN
 
    As discussed above, we are engaged in an ongoing year 2000 assessment and
have not yet developed any contingency plans. The results of our year 2000
testing, which is expected to be completed by the end of April 1999, and the
responses received from third-party vendors and service providers will be taken
into account in determining the nature and extent of any contingency plans.
 
                                       32
<PAGE>
                                    BUSINESS
 
INTRODUCTION
 
    We provide Internet audience measurement products and services to leading
Internet advertisers and advertising agencies, Internet properties, technology
companies and financial institutions. We measure usage of the entire Internet,
including its largest segments, the World Wide Web and proprietary on-line
services like America Online. Our products and services enable the continued
growth and development of the Internet by providing third-party audience
measurement data that our customers rely on to make critical business decisions.
We collect these data by measuring Internet usage from a representative sample,
or panel, of personal computer users with our proprietary tracking technology.
We maintain a large panel of Internet users reporting Internet usage both at
work and at home, as well as the usage of proprietary on-line services.
 
    We have been at the forefront of the development and coordination of
technology and standards needed to facilitate advertising and transactions
between companies doing business over the Internet. The quality and depth of our
customer base and our customer renewal rate of over 95% reflect our position as
a widely accepted Internet audience measurement service.
 
INDUSTRY BACKGROUND
 
    GROWTH OF THE INTERNET
 
    The Internet has emerged as a global medium that allows millions of people
worldwide to obtain information, communicate and conduct business
electronically. The largest segments of the Internet are the Web and proprietary
on-line services, like America Online. International Data Corporation, or IDC,
estimates that the number of Web users worldwide will grow from approximately
68.7 million in 1997 to approximately 319.8 million by the end of 2002.
Additionally, America Online, the largest on-line service provider, had
approximately 16 million service subscribers at the end of 1998. The continued
growth in Internet usage will be driven by:
 
    - the large and growing number of personal computers installed in homes and
      offices;
 
    - easier, faster, more reliable and less expensive access to the Internet;
 
    - the availability of more and better content on the Internet;
 
    - the increased use of the Internet to buy and sell products and services;
 
    - improvements in network infrastructure;
 
    - the increasing ability to access the Internet with devices like
      televisions and telephones; and
 
    - the increasing familiarity and acceptance of the Internet by businesses
      and consumers.
 
    GROWTH OF INTERNET ADVERTISING AND ELECTRONIC COMMERCE
 
    The unique interactive nature of the Internet has led to its rapid emergence
as a compelling vehicle for advertisers. The Internet offers advertisers the
ability to target:
 
    - people with specific sets of interests;
 
    - users with desirable demographic characteristics; and
 
    - populations within specific regions, localities or countries.
 
    The Internet also gives marketers the potential to:
 
    - establish dialogues and individual relationships with customers;
 
                                       33
<PAGE>
    - receive direct feedback on their advertising;
 
    - quickly and cost-effectively adapt their advertising to respond to
      customer feedback; and
 
    - reach broad, global audiences.
 
    According to Forrester Research, Internet advertising spending worldwide is
expected to increase dramatically over the next five years, as illustrated by
the following chart:
 
                    WORLDWIDE INTERNET ADVERTISING SPENDING
                                ($ IN MILLIONS)
 
<TABLE>
<CAPTION>
                                 1998       1999       2000       2001       2002       2003
<S>                            <C>        <C>        <C>        <C>        <C>        <C>
North America................  $   1,300  $   2,335  $   3,995  $   5,365  $   7,775  $  10,500
Europe.......................        105        235        525      1,050      1,840      2,765
Asia/Pacific.................         80        130        250        475        815      1,245
Latin America................         20         45        110        230        420        645
                               ---------  ---------  ---------  ---------  ---------  ---------
Total........................  $   1,505  $   2,745  $   4,880  $   7,120  $  10,850  $  15,155
                               ---------  ---------  ---------  ---------  ---------  ---------
                               ---------  ---------  ---------  ---------  ---------  ---------
</TABLE>
 
    The growing adoption of the Internet also represents an enormous opportunity
for marketers to conduct commerce over the Internet. This is commonly referred
to as e-commerce. E-commerce can be fast, inexpensive and convenient. A growing
number of users have transacted business over the Internet, including trading
securities, buying goods, purchasing airline tickets and paying bills. As
business and consumer acceptance of e-commerce grows, advertisers and direct
marketers are increasingly using the Internet to locate customers, advertise and
facilitate transactions. According to IDC, e-commerce is expected to increase
dramatically over the next five years, as illustrated by the following chart:
 
                    WORLDWIDE E-COMMERCE REVENUES (WEB ONLY)
                                ($ IN MILLIONS)
 
<TABLE>
<CAPTION>
                                           1997       1998       1999       2000       2001       2002
<S>                                      <C>        <C>        <C>        <C>        <C>        <C>
E-commerce revenues....................  $  12,403  $  32,383  $  67,113  $ 132,966  $ 237,233  $ 425,730
</TABLE>
 
    The growth in Internet advertising spending will ultimately depend on the
ability of advertisers to plan their advertising expenditures by using reliable
data that demonstrate audience size and the value of Internet advertisement
placement. Timely audience measurement data have emerged as "must have"
information. This information enables the buying and selling of advertising and
sponsorship support. Additionally, reliable Internet audience measurement data
are key drivers of the e-commerce industry because they enable Internet
marketers to analyze consumer behavior and focus their Internet investments.
 
                                       34
<PAGE>
    THE NEED FOR A MEASUREMENT STANDARD
 
    Traditional media - including television, radio and print - are largely
supported by advertising spending. One of the principal elements that drives the
growth of advertising in all media is the availability of audience measurement
data, or ratings. In each medium, a single standard of audience measurement has
emerged. For over 40 years, Nielsen's estimates of televison audience size and
composition have served as the standard for audience measurement of national and
local television advertising. Arbitron serves as the radio audience measurement
standard, and MRI serves as the magazine readership measurement standard. These
third-party standards provide a uniform basis of measurement which advertisers,
media companies, ad agencies and the financial community rely on to make
critical business decisions.
 
    Given the widespread availability of essentially free information on the
Internet, it has been difficult for Web sites and proprietary on-line services
to induce people to pay for on-line content. Advertising is a critical revenue
stream for providers of on-line content and services. As Web sites and on-line
content providers seek to increase advertising revenues, and as on-line
advertisers seek to determine where they should spend their advertisement
dollars, demand is growing for reliable statistics and standardized methods to
evaluate Internet usage. As a result, a standard for Internet audience
measurement must emerge, which will:
 
    - measure a large and representative sample of Internet users;
 
    - track activity on the entire Internet, not just the Web, so that key
      properties like America Online and other proprietary on-line services and
      technologies are included;
 
    - measure the Internet audience both at work and at home, because Internet
      usage differs in these two environments; and
 
    - be unbiased and independent from advertisers and content providers.
 
    As in traditional media, an independent standard of audience measurement
must be adopted by advertisers and marketers on the Internet. A significant
business opportunity exists for the company that provides this standard.
 
THE MEDIA METRIX SOLUTION - SETTING THE STANDARD
 
    We provide products and services that are critical to the continued growth
and development of the Internet. We provide a third-party audience measurement
standard that our customers use as a basis for making effective business
decisions. We have been at the forefront of the development and coordination of
technology and standards needed to facilitate advertising and transactions
between companies doing business over the Internet. Our customers include
leading Internet advertisers and advertising agencies, Internet properties,
leading technology companies and financial institutions.
 
    We have become a widely accepted Internet audience measurement service
because of the following:
 
    WE PROVIDE COMPREHENSIVE AUDIENCE MEASUREMENT.  We are able to measure the
entire Internet audience, including people who use the Web and proprietary
on-line services, like America Online. We maintain a large panel of Internet
users reporting Internet usage at work and at home.
 
    WE DELIVER ACKNOWLEDGED EXPERTISE IN MARKETING AND MEDIA RESEARCH.  The
members of our management team are leaders in the field of Internet audience
measurement and share a vast repository of knowledge in panel-based research,
media research, media research technology, television and print media and in
various fields of marketing research. As a result, we have extensive expertise
in the development and management of representative consumer and business panels
to collect data. This is a complicated process that is performed effectively by
only a limited number of marketing research
 
                                       35
<PAGE>
companies. Panel recruitment must be managed carefully in order to construct a
panel broad enough to provide sufficient sample size and varied enough to
provide meaningful data on different population segments. Our management team's
experience in the art of managing panels results largely from its experience at
NPD, a U.S.-based marketing research firm and a provider of panel-based
marketing information.
 
    WE MEET THE NEEDS OF AN INFLUENTIAL CUSTOMER BASE.  Our success is due in
part to our large base of established client companies, including leading new
and traditional media companies, advertising agencies, technology companies,
e-commerce marketers and financial institutions. These customers are responsible
for a significant percentage of total Internet advertising revenues. As a
result, their views influence the developing standards for Internet audience
measurement. These customers rely on our data to make effective business
decisions. We work with our customers and key trade associations to gain
critical insights into evolving markets and to remain at the forefront of
ongoing changes in the industry. This allows us to continue to effectively meet
our customers' needs.
 
    WE DEMONSTRATE TECHNOLOGICAL LEADERSHIP.  We collect data through our
proprietary metering system, or meter, which is contained in a software
application installed on a panelist's personal computer. The meter monitors all
communications between the computer's operating system and the software
applications and hardware that the operating system controls and monitors. By
measuring these communications, we become aware of all activities taking place
on the computer, which we believe positions us to measure any new digital media
that may emerge. Our metering technology produces data on Internet usage,
on-line service usage and hardware and software applications usage. Once data
are collected, we construct dynamic databases from which we produce our reports.
 
    WE PROVIDE BROAD PRODUCT OFFERINGS AND DELIVERY OPTIONS.  We offer a broad
range of comprehensive, reliable and timely audience measurement products and
services. Our product offerings include both syndicated products and customized
products. Syndicated products are standardized products that appeal to a broad
range of customers. Customized products are tailored to meet individual customer
needs. We continually expand our services in anticipation of our customers'
needs and the changes and growth of the industry we serve. We offer our
customers a variety of options for delivery of our reports, including via the
Web, e-mail, computer disk and hard copy reports.
 
STRATEGY
 
    Our goal is to become the accepted standard for Internet audience
measurement. We intend to achieve this goal through the following strategies:
 
    CONTINUE OUR INDUSTRY LEADERSHIP.  We expect to continue our history of
innovation as the pioneer of Internet audience measurement. We plan to continue
to develop our market-leading technology and leverage our panel and databases to
develop broader and more in-depth products and services. We plan to remain at
the forefront of change in the industry by continuing to work closely with our
customers and by actively working with key trade associations and non-profit
organizations to establish standards for Internet audience measurement.
 
    DEVELOP PRODUCTS TO ACCELERATE E-COMMERCE GROWTH.  We believe that the
success and growth of e-commerce, like Internet advertising, will be driven
largely by the availability of comprehensive and reliable quantitative and
qualitative data. These data must provide key statistics for the evaluation of
e-commerce businesses and business strategies. We are working with our clients
to develop products that will enable our clients to target Internet users most
likely to engage in e-commerce by providing behavioral and demographic data on
people who purchase products, actively shop, or merely click on to a particular
e-commerce site.
 
                                       36
<PAGE>
    EXPAND AND INCREASE PENETRATION OF OUR CLIENT BASE.  We will continue to add
new customers, build on our successful client retention strategy and further
expand our existing customer relationships by offering products and services
that are valuable to our customers. We have historically retained substantially
all of our client base from year to year. Of our customers under contract at the
end of 1997, over 95% remained customers at the end of 1998. We anticipate
expanding our client base as Internet advertising spending and e-commerce
transactions increase and as more Internet related businesses and advertisers
require audience measurement data.
 
    EXPAND INTERNATIONALLY.  Unlike most media, which are delivered to a
national or local market, the Internet is the first medium that is regularly
delivered to a worldwide audience. For this reason, integrated, worldwide
audience measurement will be critical for advertisers to understand whom they
are reaching and for media properties to be able to effectively sell their
available advertising inventory. Additionally, over the next five years,
Internet advertising spending growth rates worldwide are projected to exceed
spending growth rates in the United States alone. We are responding to the
demands of our customers to obtain reliable Internet audience measurement data
in key non-U.S. markets. To capitalize on this trend, we intend to leverage our
proprietary panel, technology and brand recognition to become a worldwide
provider of Internet audience measurement services. We intend to rapidly expand
our presence in the international marketplace by developing additional products
in conjunction with local strategic partners who are leaders in panel-based
marketing and media research. In April 1999, we entered into an agreement in
principle with two leading European media research and marketing information
firms to create Media Metrix Europe. Audience data collection is expected to
begin in the third quarter of 1999 in Germany, the United Kingdom and France.
 
    DEVELOP NEW PRODUCTS AND SERVICES.  In addition to e-commerce related
products, we intend to continue to develop new products and services to meet the
growing needs of our customer base. As of March 31, 1999, we employed 19 people
in new product development. We intend to expend significant additional
resources, including a portion of the proceeds from this offering, to expand our
new product development efforts. We are developing products that will offer
qualitative data measurement and expanded local market coverage. We are also
developing additional products and services based on our ability to gather
real-time data. We also intend to increase sales of customized products and
services to present and future clients. In addition, we intend to leverage the
capabilities of our patented metering method by creating and developing new
products based on a database that contains information on each panelist's
system's hardware configuration and software usage.
 
PRODUCTS AND SERVICES
 
    Our principal products and services are derived from data collected from our
panel and stored in our core databases, which we use to produce the following:
 
    - syndicated Internet audience measurement reports and services;
 
    - customized Internet audience measurement reports and services; and
 
    - hardware and software technology usage measurement reports and services.
 
                                       37
<PAGE>
    SYNDICATED PRODUCTS.  We provide syndicated Internet audience measurement
products and services as our core business. Our key syndicated products consist
of:
 
<TABLE>
<CAPTION>
PRODUCT                               DESCRIPTION
<S>                                   <C>
THE WEB REPORT......................  Our flagship syndicated audience measurement product contains the following
                                      two components:
 
                                      - THE KEY MEASURES REPORT: provides measures for all reportable Web sites,
                                      categorized within major sectors. Key measures include:
                                      - unique visitors;
                                      - the percentage of the total Web audience in a month that could be reached
                                        via each reported Web site, commonly referred to as reach;
                                      - average usage days per user;
                                      - average unique Web pages visited per day and per month;
                                      - age and gender composition; and
                                      - demographic composition.
 
                                      - THE TREND REPORT: provides information on trends within the sectors in
                                      the Key Measures Report for a six-month period. One section of the Trend
                                      Report includes trends over a three-month period for key measures. Another
                                      section provides an alphabetical listing of over 10,000 measured Web sites
                                      and properties and the reach trends for each during the relevant six-month
                                      period.
 
THE DIGITAL MEDIA REPORT............  Provides measurement of audience usage of proprietary on-line services like
                                      America Online, push technology like PointCast that delivers pre-defined
                                      content to users, other proprietary services like Juno, as well as all
                                      information collected in the Web Report. Allows for the comparison of all
                                      digital media. Measures reported include:
                                      - unique visitors;
                                      - reach;
                                      - usage days per person;
                                      - minutes per usage day and per month; and
                                      - age and gender composition.
 
THE LOCAL MARKET REPORT.............  Tracks national and local market reach, demonstrating how national and
                                      local Web sites perform within each of 14 top local markets. Data are
                                      compiled on a monthly basis. We intend to expand our coverage to 25 local
                                      markets in 1999.
 
THE AD NETWORK REPORT...............  Details reach, frequency and demographic information across ad sales
                                      networks and other ad-supported networks like DoubleClick, 24/7 Media,
                                      Flycast, LinkExchange and AdSmart. The measures reported include the full
                                      network reach and reach of those Web pages where ads have been served.
 
LIFEGRAPHICS........................  Provides behavioral data for lifestyles and purchase tendencies of Web
                                      users.
 
WEEKLY FLASH........................  Tracks web site performance on a weekly basis.
</TABLE>
 
    Currently, we also capture some information about ad banners and use it as
input to our Ad Network Report and to our customized services, reports and
analyses. Ad banners are the primary
 
                                       38
<PAGE>
format for delivering advertisements over the Internet. In the future, we may
provide a report on ad banner usage.
 
    In addition, we intend to introduce an e-commerce product line in the second
quarter of 1999. The first report that we expect to offer is the Online Shopping
Report, which will detail shopping behavior on Internet sites for selected
shopping categories.
 
    CUSTOMIZED SERVICES, REPORTS AND ANALYSES.  We leverage our vast database of
information on Internet usage and technology usage to provide clients with a
broad range of special services, reports and analyses, including the following:
 
<TABLE>
<CAPTION>
PRODUCT                               DESCRIPTION
<S>                                   <C>
 
INDUSTRY SECTOR/VERTICAL MARKET
  REPORTS...........................  Report in-depth information on Web site performance within a specific
                                      industry sector or vertical market.
 
RETENTION ANALYSES..................  Report the percentage of audience that visits a Web site during a
                                      particular month and returns during following months.
 
USAGE REPORTS.......................  Segment Web and Web site traffic into heavy, medium and light usage groups
                                      and compares behavior, usage pattern and demographics.
 
SITE CONTENT REPORTS................  Analyze specific user-defined content areas, or channels, within a Web site
                                      and reports on all items in the Key Measures Report.
 
PERSONAL CLICKSTREAM REPORTS........  Report actual click-by-click, page level behavior of a sample of users
                                      within a particular Web site as well as their behavior across the entire
                                      Web.
 
TRAFFIC REFERRAL REPORTS............  Report a summary of Web sites that users visit just prior to visiting a
                                      particular Web site and indicates where they go after exiting the site.
 
SITE INTERACTION REPORTS............  Quantify the degree to which a Web site shares audience with other Web
                                      sites and properties, detailing exclusive and duplicated audience share.
</TABLE>
 
    TECHNOLOGY USAGE MEASUREMENT REPORTS.  Our meter captures data on all
software applications used each time a panelist logs onto his or her computer.
The meter also captures data on all hardware configurations and software
availability on the user's computer. We use these data to compile reports on
technology usage for companies that develop and market hardware and software
applications and for Web sites that seek to understand the technical
specifications of their visitors' computer systems.
 
<TABLE>
<CAPTION>
PRODUCT                               DESCRIPTION
<S>                                   <C>
 
HARDSCAN REPORT                       HardScan, SoftScan and SoftUsage Reports provide details on hardware
SOFTSCAN REPORT                       ownership, peripheral ownership, branding information, installed
SOFTUSAGE REPORT                      applications and system software, including Internet browsers, and use of
LINKAGE REPORTS                       software applications categorized by Software Publishers' Association
US CONSUMER PC REPORT                 segments. The analyses in the Linkage Reports and the US Consumer PC Report
                                      provide a unique look at the relationships between hardware, software,
                                      media, ownership and usage.
</TABLE>
 
                                       39
<PAGE>
CUSTOMERS
 
    We have over 350 customers who use our data for many purposes like planning,
buying and selling advertising; developing e-commerce strategies; understanding
consumer behavior; gaining competitive market intelligence; and analyzing
investment decisions. Our customers are typically leaders in their respective
fields, and include the following:
 
<TABLE>
<CAPTION>
CLIENT SECTOR                         TYPICAL CLIENTS
<S>                                   <C>
 
Media Organizations.................  All of the top 20 Internet properties, including America Online, Buena
                                      Vista/Disney, Excite, GeoCities, Infoseek, Lycos, Netscape, Time Warner and
                                      Yahoo!
 
Advertising Agencies................  Interpublic Group, J. Walter Thompson, Modem Media.Poppe Tyson, Omnicom and
                                      Young & Rubicam
 
Advertisers and Marketers...........  Amazon.com, CDNow, eBay and General Motors
 
Technology Companies................  AT&T, Compaq, GTE, Hewlett-Packard, IBM and Microsoft
 
Financial Community.................  E*TRADE, Fidelity, Goldman Sachs and Morgan Stanley Dean Witter
</TABLE>
 
    We typically enter into 12-month or longer subscription contracts with our
customers, some of whom are covered by multi-client master contracts with parent
corporations, like Time Warner and Buena Vista/Disney, to provide standard,
syndicated products and services or customized reports and analyses. It is
typical for our customers initially to purchase one of our standard products and
to upgrade over time. Of our customers under contract at the end of 1997, over
95% remained customers at the end of 1998.
 
MARKETING AND SALES
 
    A critical element of all of our marketing efforts is to build awareness of
the Media Metrix brand. Our Internet audience measurement data receive extensive
publicity due to press reporting of Internet activity which either references or
is based on our data. Other publicity is generated through public relations
activity and public speaking engagements by our executive officers.
 
    We sell and market our products through our direct sales force, which was
comprised of 19 sales representatives as of March 31, 1999. A portion of our
sales force is dedicated to servicing and maintaining current clients. The
remainder is dedicated to developing new clients. Our sales force operates out
of our New York, San Francisco and Atlanta offices. Sales representatives
receive a base salary and are eligible for commissions based on revenues and
sales goals.
 
INTERNATIONAL OPERATIONS
 
    We believe that the ability to offer Internet audience measurement data for
non-U.S. markets will be a critical element in the Internet audience measurement
market. Having established our business model in the United States, we have
begun our international expansion efforts. In April 1999, we entered into an
agreement in principle to launch Media Metrix Europe in partnership with
European media research companies GfK AG of Germany and IPSOS S.A. of France.
Media Metrix Europe will be a majority-owned subsidiary of Media Metrix. We
expect to begin audience data collection in Germany, France and the United
Kingdom in the third quarter of 1999. Our partners in Media Metrix Europe intend
to expand our services to other major European markets as demand warrants. We
are already measuring Internet audiences in Sweden through the SIFO Group, under
a license entered into in 1998 covering Sweden, Norway and Finland. In addition,
a Kanji version of our meter is being beta tested in Japan by a major audience
measurement company.
 
                                       40
<PAGE>
AUDIENCE MEASUREMENT METHODOLOGY
 
    Our methodology has been developed from our background in panel recruitment
and management and includes our proprietary measurement technology. Key elements
of our methodology include:
 
    PANELS AND DATA COLLECTION.  Our panel is a representative sample of
personal computer users, including at-home and at-work users. We recruit panels
by random direct mail and telephone solicitation, both of which are standard
recruitment methods in marketing research. Our panel currently consists of over
40,000 individuals under continuous measurement. In connection with our panel
recruitment process, each panelist is required to fill out a detailed
questionnaire to provide background demographic information. The questionnaire
provides information such as age, gender, household income, geographic region,
level of education, size of household and job classification of the panelists.
 
    Our proprietary metering system, or meter, is a software application
installed on a panelist's personal computer. It monitors activity of the
personal computer's operating system and browser. The meter passively records
what users do on their personal computers on a second-by-second basis,
including:
 
    - the start and stop time of each activity;
 
    - which application is being used;
 
    - detailed usage activity for proprietary on-line services; and
 
    - page-by-page viewing on the Internet.
 
    We collect the data we need for our products and services without any
agreement or arrangement with operators of Web sites or operators of proprietary
on-line services like America Online. Because we measure our panelists' computer
usage and not activity at a particular Web site or proprietary service, no
agreements with the operators of Web sites or on-line services are necessary.
 
    Once the meter has collected the data from the panelist's personal computer,
data are transmitted to our offices for processing either via disk or via
automatic transfer over the Web. We plan to introduce a new version of our
metering system in 1999. The new meter will capture additional details of
Internet usage to accurately report audience behavior of emerging media such as
streaming audio and video. This version will also provide real time transmission
of data on usage. We also collect data via questionnaires distributed through
direct mail and over the Web. We utilize our own software to collect information
on hardware configurations and software installations of our panelists.
 
    The statistical quality of the information that we collect is a function of
minimizing both sampling error and measurement error. Sampling error is a
function of the size and quality of the sample. Measurement error is a function
of the scope of the universe under measurement. We minimize sampling error by
maintaining a large panel. We minimize measurement error by measuring all
Internet usage, including the Web, proprietary on-line services like America
Online and all other activity on our panelists' personal computers.
 
    DATA ANALYSIS AND REPORT GENERATION AND DELIVERY.  Data retrieved from the
meter are transmitted or downloaded to file servers and then combined with those
of all the other panelists. The data are then used to construct several
databases, which we use to provide our reports. We deliver our reports in one or
more of the following formats: via proprietary Web-based delivery systems;
e-mail; computer disk or hard copy.
 
OPERATIONS AND TECHNOLOGY
 
    We have built our primary data collection, retrieval and processing system
based on systems and software developed by NPD. Our system has been designed
around industry standard data architectures. Backup procedures are built into
the processing environment in order to reduce downtime in the
 
                                       41
<PAGE>
event of outages or catastrophic occurrences. Our hardware systems are hosted at
NPD's Uniondale, New York facility, our Atlanta, Georgia facility, NPD's Port
Washington, New York facility, and at two offsite professionally-managed
computer centers in Atlanta, Georgia and Santa Clara, California. We outsource
the operation of much of our technical infrastructure to NPD.
 
    As of March 31, 1999, we had 19 employees dedicated to research and
development. We incurred research and development expenses of $588,000 in 1996,
$865,000 in 1997, $1.4 million in 1998 and $681,000 in the three months ended
March 31, 1999. We anticipate that we will continue to devote significant
resources to product development and the development of delivery technology in
the future as we add new reports and databases.
 
INTELLECTUAL PROPERTY
 
    We regard the protection of our patents, copyrights, service marks,
trademarks and trade secrets as important to our future success and rely on a
combination of patent, copyright, trademark, service mark and trade secret laws
and contractual restrictions to establish and protect our proprietary rights. We
require all employees and contractors to enter into confidentiality and
invention assignment agreements, and we enter into nondisclosure agreements with
third-parties with whom we do business in order to limit access to and
disclosure of our proprietary information. We cannot assure you that these
contractual arrangements or the other steps we have taken or will take in the
future will be sufficient to protect our technology from infringement or
misappropriation or to deter independent development of similar or superior
technologies by others.
 
    We seek to obtain the issuance of patents and the registration of our
trademarks and service marks in the United States and in selected other
countries. Effective patent, trademark, service mark, copyright and trade secret
protection may not be available in every country in which our products and
services are or will be made available. We also expect to license proprietary
rights such as patents, trademarks or copyrighted material to strategic partners
in the course of our planned international expansion. While we will attempt to
ensure that the quality of our service is maintained by such licensees, we
cannot assure you that such licensees will not take actions that might
materially adversely affect the value of our proprietary rights or reputation,
which could have a material adverse effect on our business, results of
operations and financial condition.
 
    We also rely on certain technologies that we license from third parties,
like NPD, which licenses to us key software products and database technology. We
cannot assure you that these third-party technology licenses will not infringe
the proprietary rights of others or will continue to be available to us on
commercially reasonable terms, if at all. The loss of such technology could
require us to obtain substitute technology of lower quality or performance
standards or at greater cost, which could materially adversely affect our
business, results of operations and financial condition.
 
    We have been issued a patent in the United States with regard to our meter
methodology. We also have patent applications pending in the European Patent
office and in Australia, Brazil, Canada, Japan, Mexico, Norway and the United
States.
 
    We have also applied for a patent in the United States and other foreign
jurisdictions on the methodology for monitoring of remote data access on a
public computer network which comprises the former RelevantKnowledge meter. This
application is currently pending.
 
    In connection with our federal trademark application for the name "Media
Metrix," a third party has filed an opposition to our application.
 
    To date, we have not been notified that our technologies infringe the
proprietary rights of third parties. We cannot assure you that others will not
claim that we have infringed proprietary rights with respect to past, current or
future technologies. We expect that the number of infringement claims in our
market will increase as the number of services and competitors in our industry
grows. Any of those
 
                                       42
<PAGE>
claims, whether meritorious or not, could be time-consuming, result in costly
litigation or require us to enter into royalty or licensing agreements. Royalty
or licensing agreements might not be available on terms we find acceptable or at
all. As a result, any such claim could have a material adverse effect upon our
business, results of operations and financial condition.
 
COMPETITION
 
    The market for measurement services for Internet technologies is new,
rapidly evolving and competitive. We expect that competition will intensify in
the future. We compete with other providers of Internet audience measurement
services, which are considered either consumer-centric measurement services or
site-centric measurement services. Consumer-centric services track usage among a
sample of users to provide an account of overall Internet usage behavior.
Site-centric services measure activity at a single web site and provide
measurement of activity at a particular Web site. We are a consumer-centric
service and compete directly with other consumer-centric measurement services
and indirectly with operators of site-centric measurement systems.
 
    Currently, we compete directly with NetRatings. NetRatings announced a
strategic relationship with Nielsen Media Research in October 1998. In March
1999, NetRatings and Nielsen Media Research introduced a new Web site ratings
service that competes directly with many aspects of our services. Nielsen Media
Research is the leading provider of television audience measurement services and
has significantly more financial and other resources than we do. In light of
these events, the Nielsen/NetRatings venture will likely become a significant
competitor. Other potential competitors include PC Data, a marketing research
firm that provides research on personal computer software and hardware sales,
and @Plan, a consumer-centric, qualitative measurement service.
 
    In addition, we may face competition from individual Web sites that may
develop new and independent methods of measuring their own audience. We also
face competition from other companies that develop alternative audience
measurement technologies to those already provided by us or our current
competitors. Competitive pressures created by any one of these companies, or by
our competitors collectively, could have a material adverse effect on our
business, results of operations and financial condition.
 
    We believe that the principal competitive factors in our market are the
ability to:
 
    - create high-quality, timely and reliable consumer and business panels of a
      sufficient size and representative nature to provide the necessary data;
 
    - provide measurement services of proprietary on-line services and
      Internet-related activity as well as measuring Web activity; and
 
    - establish credibility and provide a trusted independent source of data.
 
    Some of our competitors and potential competitors have longer operating
histories, larger customer bases and greater brand recognition in other
businesses and significantly greater financial, marketing, technical and other
resources than we do. We also face competition in the area of development of
representative consumer and business panels to provide data. In addition, other
measurement services may be acquired by, receive investments from or enter into
other commercial relationships with larger, well-established and well-financed
companies as use of the Internet increases. Therefore, certain of our
competitors with other revenue sources may be able to devote greater resources
to marketing and promotional campaigns, adopt more aggressive pricing policies
and devote substantially more resources to technology and systems development
than we can. Increased competition may result in reduced operating margins, loss
of market share and diminished value in our services. We cannot assure you that
we will be able to compete successfully against current and future competitors.
Further, as a strategic response to changes in the competitive environment, we
may, from time to time, make certain pricing, service or marketing decisions or
acquisitions that could have a material adverse effect
 
                                       43
<PAGE>
on our business, results of operations and financial condition. New technologies
and the expansion of existing technologies may also increase the competitive
pressures on us by enabling our competitors to offer a lower-cost service.
 
EMPLOYEES
 
    As of March 31, 1999, we had 95 full-time employees, with:
 
    - 19 in research and development;
 
    - 27 in operations;
 
    - 37 in sales, marketing and client service; and
 
    - 12 in management, administration and finance.
 
    Our employees are not covered by a collective bargaining agreement. We have
never experienced an employment-related work stoppage and consider our employee
relations to be good.
 
PROPERTIES
 
    Currently, our operations and research and development facility is located
in Uniondale, New York, which is leased to us by NPD under the terms of a
management services agreement. See "Certain Transactions--Management Services
Agreement." In addition, we lease office space in Atlanta, Georgia, San
Francisco, California, and New York, New York. We also sublease additional
office space at another location in New York, New York. We are in negotiations
with a third party to lease additional space in New York, New York.
 
LEGAL PROCEEDINGS
 
    We are not a party to any material legal proceedings.
 
                                       44
<PAGE>
                                   MANAGEMENT
 
OUR EXECUTIVE OFFICERS, KEY EMPLOYEES AND DIRECTORS
 
    The executive officers, key employees and directors of Media Metrix, and
their ages and positions, are:
 
<TABLE>
<CAPTION>
NAME                                         AGE                                   POSITION
<S>                                      <C>          <C>
Tod Johnson............................          54   Chairman of the Board, Chief Executive Officer and Director
 
Mary Ann Packo.........................          44   President and Chief Operating Officer
 
Steve Coffey...........................          43   Executive Vice President
 
Thomas A. Lynch........................          38   Chief Financial Officer, Secretary and Treasurer
 
Doug McFarland.........................          49   Senior Vice President, Sales
 
Jeffrey C. Levy(1).....................          36   Director and Vice Chairman
 
Michael C. Brooks(2)...................          54   Director
 
Stig Kry(2)............................          70   Director
 
William W. Helman(1)...................          40   Director
 
James Mortensen(1)(2)..................          73   Director
 
Timothy F. S. Cobb(3)..................          34   Executive Consultant
</TABLE>
 
- -----------------------
 
(1) Compensation committee member.
 
(2) Audit committee member.
 
(3) Not an executive officer.
 
    TOD JOHNSON has been our Chairman of the Board and Chief Executive Officer
since March 1997 and has been involved in managing our business since our
inception as a division of NPD and then as PC Meter. He is the principal
shareholder of NPD and has served as the Chairman and Chief Executive Officer of
NPD since 1971. He has also served as Chairman of the Advertising Research
Foundation and was the Founding Co-Chairman of the Council for Marketing and
Opinion Research. Mr. Johnson earned a B.S. and an M.S. from Carnegie Mellon
University.
 
    MARY ANN PACKO has been our President and Chief Operating Officer since
March 1997. She has been involved in managing our business since July 1996. She
served as Executive Director of IPSOS-NFO Europe, Paris, from July 1995 to July
1996 and as Vice President of New Ventures with NFO Worldwide from July 1994 to
July 1995. Prior to July 1994, Ms. Packo was the President of the Custom
Services Division of NPD Canada. Ms. Packo co-founded and was President of
National Yellow Pages Monitor and has served on the Board of Directors of the
Internet Advertising Bureau. Ms. Packo received her B.S. from Miami University,
Oxford, Ohio.
 
    STEVE COFFEY has been our Executive Vice President since 1997 and has been
involved in managing our business since our inception as a division of NPD and
then as PC Meter. Mr. Coffey also headed the Advanced Research and Development
team at NPD from October 1994 to January 1996, where he founded and launched PC
Meter. Mr. Coffey received an M.S. from Columbia Business School.
 
    THOMAS A. LYNCH has been our Chief Financial Officer since March 1997 and
has been involved in managing our business since our inception as a division of
NPD and then as PC Meter. He also served as Senior Vice President and Chief
Financial Officer of NPD from May 1995 to November 1998. Prior to joining NPD,
Mr. Lynch was a partner at KPMG Corporate Finance in Tokyo, Japan, from 1992 to
May 1995. Mr. Lynch earned a Bachelors of Commerce degree from University
College Dublin, Ireland and an M.B.A. from the London Business School, England.
 
                                       45
<PAGE>
    DOUG MCFARLAND has been our Senior Vice President, Sales since February
1997. From July 1994 until joining us, Mr. McFarland was an executive vice
president with FreeMark Communications. From February 1992 until July 1994, Mr.
McFarland was a senior vice president of Next Century Media. Prior to that time,
he held various positions at Arbitron, including vice president-sales and
marketing. Mr. McFarland received his B.A. from Emory and Henry College and an
M.A. from Virginia Tech.
 
    JEFFREY C. LEVY has been a director and Vice Chairman since November 1998.
Mr. Levy co-founded RelevantKnowledge with Timothy F. S. Cobb and served as its
Chief Executive Officer from November 1996 to November 1998. He served as legal
counsel at Turner Broadcasting System, Inc. from January 1995 to November 1996.
From July 1992 to January 1995, he was an associate at the law firm of Dow,
Lohnes & Albertson. Mr. Levy holds an A.B. from Harvard College and a J.D. from
Harvard Law School.
 
    MICHAEL C. BROOKS has been a director since November 1998. He was a director
of RelevantKnowledge prior to the merger. He has been a general partner of J.H.
Whitney & Co., a venture capital fund, since 1984. He is also a director of
SunGard Data Systems, Inc., Pegasus Communications, Inc., NMT Medical,
USinternetworking, Inc. and several other private companies. Mr. Brooks holds a
B.A. from Yale College and an M.B.A. from Harvard Business School.
 
    WILLIAM W. HELMAN has been a director since April 1997. He has been a
general partner of Greylock IX Limited Partnership, a venture capital fund,
since 1984. He is also a director of Millennium Pharmaceuticals, Inc., Vertex
Pharmaceuticals, Inc. and various privately held companies. Mr. Helman holds an
A.B. from Dartmouth College and an M.B.A. from Harvard Business School.
 
    STIG KRY has been a director since March 1997. He has been employed by Kurt
Salmon Associates, Inc., a management consulting firm, since 1958, holding
various positions, including Chief Executive from 1975 to 1987 and his current
position as Chairman Emeritus since 1993. He is a director of Guilford Mills,
Inc. and Osh Kosh B'Gosh, Inc. as well as several private companies. Mr. Kry is
a member of NPD's Board of Advisors. Mr. Kry holds a degree in textile
engineering from NKI, Skolan, Stockholm, Sweden.
 
    JAMES MORTENSEN has been a director since March 1997. Mr. Mortensen has been
a private consultant since 1982. He was employed by Young & Rubicam Inc. from
1957 to 1982 where he held various positions, including Chief Financial Officer,
Vice Chairman and Chair of the Executive Committee. Mr. Mortensen is a member of
NPD's Board of Advisors. Mr. Mortensen attended Denver University.
 
    TIMOTHY F. S. COBB is an executive consultant and former director. He was a
director from November 1998 through February 1999. He co-founded
RelevantKnowledge with Jeffrey C. Levy and served as its President from November
1996 to November 1998. Prior to founding RelevantKnowledge, Mr. Cobb held
various positions at Turner Broadcasting System, Inc. from March 1994, including
Vice President-- Business Ventures and legal counsel. Mr. Cobb holds a B.S. from
the University of North Carolina at Chapel Hill and a J.D. from the University
of Pennsylvania Law School.
 
    After the closing of this offering, our board will be divided into three
classes, denominated Class I, Class II and Class III. Members of each class hold
office for three-year terms which are staggered. At each annual meeting of our
stockholders starting with the meeting in 2000, the successors to the directors
whose terms expire at that meeting will be elected to serve for a three-year
period following their election or until a successor has been duly elected and
qualified. Messrs. Levy and Mortensen are Class I directors whose terms expire
at the 2000 annual meeting of stockholders. Messrs. Brooks and Kry are Class II
directors whose terms expire at the 2001 annual meeting of stockholders. Messrs.
Johnson and Helman are Class III directors whose terms expire at the 2002 annual
meeting. The expiration of a director's term is subject in all cases to the
election and qualification of his successor or his earlier death, removal or
resignation. All of our directors were elected to the board pursuant to a
 
                                       46
<PAGE>
stockholders' agreement, which will terminate at the closing of the offering.
Our officers are appointed to serve at the discretion of the board.
 
    The board has established an audit committee and a compensation committee.
The audit committee reviews our annual audit and meets with our independent
auditors to review our internal controls and financial management practices. The
compensation committee recommends to the board the compensation for our key
employees.
 
DIRECTOR COMPENSATION
 
    In the past, non-employee, non-stockholder directors have received cash
compensation of $6,000 per year and options to purchase our common stock
received from both NPD and Media Metrix. See "Principal Stockholders." We intend
to institute a policy of compensation for non-employee directors prior to the
offering.
 
EXECUTIVE COMPENSATION
 
    The following table sets forth information concerning all cash and non-cash
compensation awarded to, earned by or paid to our Chief Executive Officer and
our next four most highly compensated executive officers for services rendered
to us during the fiscal year ended December 31, 1998.
 
                           SUMMARY COMPENSATION TABLE
 
<TABLE>
<CAPTION>
                                                                                                        LONG-TERM
                                                                                                       COMPENSATION
                                                                  ANNUAL COMPENSATION           --------------------------
                                                          ------------------------------------  SECURITIES
                                                                                     OTHER      UNDERLYING        ALL
             NAME AND PRINCIPAL                                                     ANNUAL       OPTIONS/        OTHER
                  POSITION                       YEAR       SALARY      BONUS    COMPENSATION      SARS      COMPENSATION
<S>                                            <C>        <C>         <C>        <C>            <C>          <C>
Tod Johnson..................................       1998      --         --        $  62,000(1)     --            --
  Chief Executive Officer and                       1997      --         --           62,000(1)     --            --
  Chairman of the Board (1)                         1996      --         --           --            --            --
 
Mary Ann Packo...............................       1998  $  157,500  $  59,000       --            43,715        --
  President and Chief                               1997     153,000     35,000       --            26,092        --
  Operating Officer                                 1996(2)     62,500    51,000      --            66,534        --
 
Steve Coffey.................................       1998     145,000     54,500       --            43,715        --
  Executive Vice President                          1997     130,000     35,000       --            26,092        --
                                                    1996     120,000     47,000       --            66,534        --
 
Thomas A. Lynch..............................       1998      --         --        $  36,000(1)     39,366        --
  Chief Financial Officer (1)                       1997      --         --           36,000(1)      2,174        --
                                                 1996         --         --           --            --            --
 
Doug McFarland...............................       1998     154,500     42,000       --            30,555        --
  Senior Vice President, Sales                      1997     150,000     30,000       --            36,963        --
                                                 1996         --         --           --            --            --
</TABLE>
 
- -----------------------
 
(1) Compensation for Mr. Johnson's services as Chief Executive Officer and Mr.
    Lynch's services as Chief Financial Officer in 1998 was paid under our
    management services agreement with NPD. NPD was reimbursed $62,000 for Mr.
    Johnson's services in each of the years 1997 and 1998. NPD was reimbursed
    $36,000 for Mr. Lynch's services in each of the years 1997 and 1998. We will
    continue to pay for Mr. Johnson's services pursuant to an amended and
    restated management services agreement at the rate of $15,000 per month. See
    "Certain Transactions--Transactions with Officers and Directors--Management
    Services Agreement." Mr. Lynch's salary was paid by NPD through December
    1998. For 1999, Mr. Lynch is being paid at the rate of $165,000 per annum.
 
(2) Ms. Packo joined us in July 1996.
 
                                       47
<PAGE>
STOCK OPTIONS
 
    The following table sets forth summary information concerning individual
grants of stock options made during the year ended December 31, 1998 to each of
our executive officers named in the Summary Compensation Table.
 
                 OPTION GRANTS IN YEAR ENDED DECEMBER 31, 1998
<TABLE>
<CAPTION>
                                                            INDIVIDUAL GRANTS                                  POTENTIAL REALIZABLE
                              ------------------------------------------------------------------------------     VALUE AT ASSUMED
                               NUMBER OF    % OF TOTAL                                                        ANNUAL RATES OF STOCK
                                SHARES       OPTIONS      EXERCISE     DEEMED VALUE                             PRICE APPRECIATION
                              UNDERLYING    GRANTED TO     OR BASE     PER SHARE ON                            FOR OPTION TERM (3)
                                OPTIONS    EMPLOYEES IN   PRICE PER        DATE                               ----------------------
                                GRANTED        1998       SHARE (1)    OF GRANT (2)       EXPIRATION DATE         0%          5%
<S>                           <C>          <C>           <C>          <C>              <C>                    <C>         <C>
Tod Johnson.................      --            --           --             --                  --                --          --
 
Mary Ann Packo..............      21,743          11.7%   $    2.30      $    2.30         July 22, 2008          --      $   31,450
                                  21,972                       2.39          10.29          December 3, 2008  $  173,579     315,767
 
Steve Coffey................      21,743           11.7        2.30           2.30         July 22, 2008          --          31,450
                                  21,972                       2.39          10.29          December 3, 2008     173,579     315,767
 
Thomas A. Lynch.............      17,394           10.5        2.30           2.30         July 22, 2008          --          25,160
                                  21,972                       2.39          10.29          December 3, 2008     173,579     315,767
 
Doug McFarland..............      19,569            8.2        2.30           2.30         July 22, 2008          --          28,306
                                  10,986                       2.39          10.29          December 3, 2008      86,789     157,883
 
<CAPTION>
 
                                 10%
<S>                           <C>
Tod Johnson.................      --
Mary Ann Packo..............  $   79,701
                                 533,911
Steve Coffey................      79,701
                                 533,911
Thomas A. Lynch.............      63,760
                                 533,911
Doug McFarland..............      71,732
                                 266,956
</TABLE>
 
- -----------------------
 
(1) The exercise prices represent our board's estimate of the fair market value
    of the common stock on the grant date. The board considered many factors in
    establishing such prices, including our financial condition and operating
    results, an independent valuation and the market for Internet-related
    stocks.
 
(2) The deemed value on the date of grant of the options granted on December 3,
    1998 was determined after the date of grant solely for financial accounting
    purposes.
 
(3) These amounts represent assumed rates of appreciation in the price of our
    common stock during the terms of the options in accordance with rates
    specified in applicable federal securities regulations. The 0%, 5% and 10%
    assumed annual rates of compounded stock price appreciation do not represent
    our estimate or projection of our future common stock prices. Each option
    listed in the table has a 10-year term. Actual gains, if any, on stock
    option exercises will depend on the future price of the common stock. There
    is no representation that the rates of appreciation reflected in this table
    will be achieved.
 
                                       48
<PAGE>
    The following table sets forth at December 31, 1998 the number of options
and the value of unexercised options held by each of the executive officers
named in the Summary Compensation Table:
 
                       AGGREGATED YEAR-END OPTION VALUES
 
<TABLE>
<CAPTION>
                                                                 NUMBER OF SHARES          VALUE OF UNEXERCISED
                                                              SUBJECT TO UNEXERCISED           IN-THE-MONEY
                                                               OPTIONS AT YEAR END       OPTIONS AT YEAR END (1)
                                                            --------------------------  --------------------------
NAME                                                        EXERCISABLE  UNEXERCISABLE  EXERCISABLE  UNEXERCISABLE
<S>                                                         <C>          <C>            <C>          <C>
Tod Johnson...............................................          --             --           --              --
 
Mary Ann Packo............................................      49,574         86,767    $ 831,356   $   1,362,615
 
Steve Coffey..............................................      49,574         86,767      831,356       1,362,615
 
Thomas A. Lynch (2).......................................         435         88,235        7,295       1,396,236
 
Doug McFarland............................................       7,393         60,125      123,981         944,058
</TABLE>
 
- -----------------------
 
(1) The dollar values have been calculated by determining the difference between
    the fair market value of the securities underlying the options at December
    31, 1998 and the exercise prices of the options. Solely for purposes of
    determining the value of options at December 31, 1998, we have assumed that
    the fair market value of shares of common stock issuable upon exercise of
    options was $17.00 per share, the initial public offering price, since the
    common stock was not traded in an established market prior to the offering.
 
(2) Includes 47,130 shares of our common stock issuable upon the exercise of
    options granted pursuant to an NPD plan that gives Mr. Lynch an option to
    purchase shares of Media Metrix common stock held by NPD.
 
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION
 
    We have established a compensation committee consisting of William W.
Helman, Jeffrey C. Levy and James Mortensen. Until February 1999, matters
concerning executive officer compensation were addressed by the entire board
because we did not have a compensation committee.
 
EQUITY INCENTIVE PLANS
 
    We adopted our 1998 Equity Incentive Plan in November 1998. Under the 1998
Plan, we may award incentive and non-statutory stock options, stock appreciation
rights, restricted stock, performance stock units and other stock units which
are valued by reference to the value of our common stock. We also maintain the
Media Metrix Stock Option Plan which provides for the award of up to 519,222
shares of our common stock in the form of incentive stock options and
non-statutory stock options. The 1998 Plan and the Media Metrix Plan are
hereinafter referred to collectively as the equity plans.
 
    In February 1999, the board adopted an amendment to the 1998 Plan to
increase the number of shares of our common stock available for awards under the
1998 Plan from 732,400 to 1,318,320.
 
    As of March 31, 1999, options to purchase an aggregate of 959,190 shares of
common stock were outstanding under the equity plans, and an aggregate of
877,587 shares of common stock are authorized but have not yet granted as awards
under the equity plans. We do not intend to issue any more options under the
Media Metrix Plan.
 
    Our officers, employees, non-employee directors and consultants are eligible
to participate in the equity plans. The compensation committee administers the
equity plans and determines, subject to the provisions of the equity plans, who
shall receive awards, the types of awards to be made, and the terms and
conditions of each award. Options that are intended to qualify as incentive
stock options under the equity plans may not be exercisable for more than 10
years after the date the option is granted and may not be granted at an exercise
price less than the fair market value of our common stock at the
 
                                       49
<PAGE>
time the option is granted. In the case of incentive stock options granted to
holders of more than 10% of our common stock, the options may not be granted at
an exercise price less than 110% of the fair market value of our common stock at
the time the options are granted.
 
    The 1998 Plan provides that all outstanding awards shall become immediately
exercisable on the day prior to the consummation of any merger or consolidation
in which we are not the surviving corporation or which results in the
acquisition of substantially all our outstanding shares by a single person or
entity or by a group of persons and/or entities acting in concert, or in the
event of the sale or transfer of substantially all of our assets. The number of
shares subject to each award shall be adjusted upon the occurrence of a stock
split or recapitalization of our common stock.
 
    The board may amend, modify or terminate any outstanding award under the
equity plans with the participant's consent, except consent shall not be
required if the board determines that such action will not materially and
adversely affect the participant. The board may amend, suspend or terminate
either of the equity plans, or any part of such plans, at any time.
 
                                       50
<PAGE>
                 CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS
 
FORMATION BY NPD
 
    Prior to April 14, 1997, the business currently conducted by Media Metrix
was operated as PC Meter. NPD originally held 100,000 Class A Limited
Partnership Units and 79,000 Class B Limited Partnership Units of PC Meter. The
1995 Scott Johnson Trust and The 1995 Stacey Johnson Trust each held 19,323.5
Class B Limited Partnership Units of PC Meter. In addition, PC Meter was
indebted to NPD in the amount of approximately $4.0 million which PC Meter used
for working capital purposes. On April 14, 1997, PC Meter was merged with and
into Media Metrix. Immediately prior to the merger, NPD purchased an additional
338,767.7324 Class A Limited Partnership Units for a purchase price of $3.2
million. Under the terms of the merger between Media Metrix and PC Meter, each
Class A Limited Partnership Unit was exchanged for 0.09446 shares of our
redeemable preferred stock for a total of 41,446 shares. Each Class B Limited
Partnership Unit was exchanged for 12.75 shares of our common stock. NPD
currently hold 41,446 shares of our redeemable preferred stock and 4,380,559
shares of common stock. Tod Johnson, our Chairman and Chief Executive Officer,
is the controlling stockholder of NPD. After the merger, we repaid the
indebtedness owed to NPD by PC Meter.
 
PRIVATE PLACEMENTS OF SECURITIES
 
    On April 14, 1997 we issued:
 
    - warrants to purchase 377,642 shares of common stock at an exercise price
      of $2.88 per share to Veronis Suhler & Associates;
 
    - 495,603 shares of Series A Preferred Stock convertible into 2,155,176
      shares of common stock, at an effective purchase price per share of common
      stock of $1.86; and
 
    - warrants to purchase 159,640 shares of Series B Preferred Stock at an
      exercise price of $12.53 per share.
 
    Of the securities issued, and after giving effect to the conversion of our
convertible preferred stock on November 4, 1998, Greylock IX Limited Partnership
purchased 1,030,743 shares of our common stock for an aggregate of $1,331,997.
Warrants to purchase 119,713 shares of Series B Preferred Stock were exercised
on November 4, 1998 and such shares of Series B Preferred Stock were converted
into 520,590 shares of common stock on the same date. Warrants to purchase
39,926 shares of Series B Preferred Stock were converted into warrants to
purchase 173,629 shares of common stock at an exercise price of $2.88 per share.
Greylock received warrants to purchase 104,175 shares of our common stock. All
of these warrants were exercised on March 31, 1999.
 
    On November 5, 1998, RelevantKnowledge merged into Media Metrix. We issued
an aggregate of 3,890,825 shares of common stock, or 0.3111 shares of common
stock for each outstanding share of common stock and preferred stock of
RelevantKnowledge. We also replaced 1,160,290 warrants to purchase shares of
RelevantKnowledge common stock with a weighted average exercise price of $2.31
with warrants to purchase 360,907 shares of our common stock with a weighted
average exercise price of $1.38. We also issued 46,775 options to purchase our
common stock to the employees of RelevantKnowledge who became our employees
after the merger. Messrs. Levy and Cobb and Whitney Equity Partners, L.P. all
received shares of our common stock in the merger.
 
TRANSACTIONS WITH DIRECTORS AND EXECUTIVE OFFICERS
 
    MANAGEMENT SERVICES AGREEMENT
 
    With the formation of PC Meter on March 31, 1996, PC Meter entered into a
management services agreement with NPD and Tod Johnson. NPD and Mr. Johnson
agreed to provide services related to PC Meter's business to the extent PC Meter
wished to use such services. We succeeded to that agreement when we merged with
PC Meter. The agreement was amended and restated on
 
                                       51
<PAGE>
April 14, 1997 in connection with the private placement of our Series A
Preferred Stock and warrants to purchase Series B Preferred Stock. We entered
into a new management services agreement with NPD and Mr. Johnson on September
30, 1998, in anticipation of our merger with RelevantKnowledge, on substantially
the same terms as the prior management services agreement. Services which NPD
agreed to provide, if needed, include:
 
    - the support of the operation and administration of our panel, including
      recruitment, operation and compensation of the panel;
 
    - access to panelists in NPD's panels;
 
    - data capture and editing of data;
 
    - data base structuring and storage of data;
 
    - processing of reports and client support;
 
    - provision of systems support and development as necessary;
 
    - provision of computer time, storage and printing as reasonably necessary
      in connection with the provision of the services specified in the
      preceding items, support in connection with client service and sales;
 
    - office space and facilities within NPD leased facilities; and
 
    - the provision of NPD's hardware ownership survey.
 
    In addition to the specific services outlined above, NPD also agreed to
provide administrative and office logistical support, including payroll
management. At this time, NPD no longer provides payroll and panel support
services.
 
    The management services agreement may be terminated by either party with 90
days' prior written notice, except that NPD may not terminate the management
services agreement prior to March 31, 2002. When the management services
agreement is terminated, NPD will provide us with a perpetual, royalty free,
non-forfeitable license of all data and documentation in its possession and
developed during the performance of the services relating to our business. We
have also agreed to provide NPD with a reciprocal license relating to data and
documentation which we generate during the performance of the services relating
to our business.
 
    NPD and Mr. Johnson have also agreed that during the term of the management
services agreement and for a period of two years after its termination, neither
NPD nor Mr. Johnson will enter into the field of audience measurement for
digital on-line media and measurement of usage of computer software and personal
computers, except for investments in publicly traded companies not to exceed 10%
of any company's outstanding capital stock.
 
    As compensation for the services provided by NPD, we pay NPD on a monthly
basis an amount equal to all expenses reasonably incurred by NPD in the
performance of its duties under the management services agreement, plus 105% of
the sum of (1) the amount of NPD's overhead allocable to us and (2) service
charges like computer rent, mail handling and printing and postage. NPD charged
us $6.0 million under the management services agreement in 1998.
 
    NPD was reimbursed $62,000 for Mr. Johnson's services in 1997 and 1998. NPD
was reimbursed $36,000 for Mr. Lynch's services in 1997 and 1998. These amounts
represent all compensation to NPD for the services provided to us by Mr. Johnson
and Mr. Lynch in 1997 and 1998. Messrs. Johnson and Lynch provided services to
NPD in addition to those related to Media Metrix and were compensated for those
services. Compensation paid by NPD to Messrs. Johnson and Lynch exceeded the
amounts paid by the Company to NPD. The amounts charged by NPD for Mr. Johnson
and Mr. Lynch's services to Media Metrix were below the amounts provided for
under the management services agreement.
 
                                       52
<PAGE>
NPD has waived any additional amounts to which it is entitled under the
agreement. See "Management--Executive Compensation."
 
    Upon the closing of this offering, we will amend and restate the management
services agreement to provide that NPD will be reimbursed $15,000 per month, or
$180,000 per year, for Mr. Johnson's services. As of January 1, 1999, Mr. Lynch
became one of our employees and we have agreed to pay him an initial yearly base
salary of $165,000.
 
    SERVICES AGREEMENT
 
    We entered into a new services agreement with NPD as of September 30, 1998
which replaced a prior services agreement having substantially similar terms. We
have granted NPD and its affiliates access to our databases for any business
purpose of NPD and its affiliates which is not in direct competition with our
business. We have also granted NPD a non-exclusive licence to use certain
computer software owned by us which is used for Internet audience measurement.
In addition, we have also agreed that we will not license our software to any
one else who will use the software to compete with NPD. Under the terms of the
services agreement, we receive a monthly fee of $2,500 plus expenses. In 1998,
we received an aggregate of $30,000 in fees and no reimbursed expenses. The
services agreement is terminable by mutual consent of the parties or on 120
days' prior written notice by either party.
 
    LICENSE AGREEMENT
 
    We entered into a new license agreement dated as of November 5, 1998 with
NPD which replaced a prior license agreement having substantially similar terms.
NPD has granted to us an exclusive, non-transferable, perpetual, worldwide
license to use some of its computer software solely in connection with the
operation of the our metering system. This software enables us to construct our
databases from the data we collect from our panelists. We pay NPD licensing fees
of $11,000 per month payable quarterly, or $132,000 per year. In 1998, we paid
NPD an aggregate of $132,000 in licensing fees. The license is terminable by NPD
on our breach of the terms of the agreement like failure to pay the license
fees, or bankruptcy.
 
    EMPLOYMENT AND CONSULTING AGREEMENTS
 
    We have entered into an employee agreement with Jeffrey C. Levy, a director
and a Vice Chairman, in connection with our merger with RelevantKnowledge. The
term of his agreement is the shorter of (1) fifteen months from November 5, 1998
and (2) six months after this offering. Mr. Levy receives an annual base salary
of $165,000 and is entitled to a bonus for 1998 and 1999 in accordance with our
bonus structure generally available for senior executives, to be determined by
the Chief Executive Officer and the non-employee director nominated by the
former stockholders of RelevantKnowledge. The agreement may be terminated with
or without cause by either party. After this offering, Mr. Levy will become a
non-executive vice chairman.
 
    At the time of our merger with RelevantKnowledge, we also entered into an
employment agreement with Timothy F. S. Cobb, the co-founder of
RelevantKnowledge, under which he acted as a Vice Chairman and a director of
Media Metrix. The agreement provides for an annual base salary of $165,000 and a
bonus for 1998 calculated in a manner similar to Mr. Levy's bonus. Following the
termination of Mr. Cobb's employment on January 31, 1999, we agreed with Mr.
Cobb that he would continue as an executive consultant.
 
LOANS TO STOCKHOLDERS
 
    In connection with the merger with RelevantKnowledge, NPD loaned $100,000 to
Jeffrey C. Levy and $100,000 to Timothy F. S. Cobb pursuant to secured
promissory notes. The notes are due and payable when Messrs. Levy or Cobb sell
shares of our common stock and receive gross proceeds of at least $500,000. The
notes bear interest at the applicable Federal rate. We anticipate that Messrs.
Levy and Cobb will repay the notes following the closing of this offering.
 
                                       53
<PAGE>
                       PRINCIPAL AND SELLING STOCKHOLDERS
 
    The following table sets forth information regarding the beneficial
ownership of our common stock as of March 31, 1999, after giving effect to the
offering, by: (1) each person known to beneficially own more than 5% of our
common stock; (2) each of our directors; (3) each executive officer named in the
summary compensation table; and (4) all executive officers and directors as a
group. Jeffrey C. Levy and Timothy F. S. Cobb each will sell up to 100,000
shares of common stock in the event the underwriters' over-allotment option is
exercised. All persons listed have sole voting and investment power with respect
to their shares unless otherwise indicated. Unless indicated otherwise, the
address of the beneficial owners is: c/o Media Metrix, Inc., 35 East 21(st)
Street, New York, New York 10010.
 
    Beneficial ownership is determined in accordance with the rules of the
Securities and Exchange Commission and generally includes voting or investment
power with respect to securities. Shares of common stock issuable pursuant to
options, to the extent those options are currently exercisable or convertible
within 60 days of March 31, 1999, are treated as outstanding for computing the
percentage of the person holding those securities but are not treated as
outstanding for computing the percentage of any other person. Unless otherwise
noted, each person or group identified possesses sole voting and investment
power with respect to shares, subject to applicable community property laws.
Beneficial ownership percentage is based on 13,727,828 shares of common stock
outstanding as of March 31, 1999 and 16,727,828 shares of common stock
outstanding after completion of this offering and in each case after giving
effect to the 1.4648-for-1 split of the common stock.
 
<TABLE>
<CAPTION>
                                                                                                  PERCENTAGE OF SHARES
                                                                                                   BENEFICIALLY OWNED
                                                                                                ------------------------
<S>                                                                                <C>          <C>          <C>
                                                                                     SHARES
                                                                                   BENEFICIALLY   BEFORE        AFTER
NAME AND ADDRESS OF BENEFICIAL OWNER                                                  OWNED      OFFERING     OFFERING
The NPD Group, Inc.(1)...........................................................   4,380,559         31.9%        26.2%
Greylock IX Limited Partnership (2)..............................................   1,193,510          8.7          7.1
The 1995 Scott Johnson Trust (3).................................................   1,071,385          7.8          6.4
The 1995 Stacey Johnson Trust (4)................................................   1,071,385          7.8          6.4
Whitney Equity Partners, L.P. (5)................................................     937,402          6.8          5.6
Oak Investment Partners VI, Limited Partnership (6)..............................     926,959          6.8          5.5
Oak VI Affiliates Fund, Limited Partnership (6)..................................     926,959          6.8          5.5
Venrock Associates II, L.P. (7)..................................................     915,826          6.7          5.5
Venrock Associates (7)...........................................................     915,826          6.7          5.5
Tod Johnson (8)..................................................................   4,380,559         31.9         26.2
Mary Ann Packo (9)...............................................................      49,574            *            *
Steve Coffey (10)................................................................      49,574            *            *
Thomas A. Lynch (11).............................................................      47,565            *            *
Doug McFarland (12)..............................................................       7,393            *            *
Jeffrey C. Levy (13).............................................................     503,204          3.7          3.0
Michael Brooks (14)..............................................................     937,402          6.8          5.6
Stig Kry (15)....................................................................      10,138            *            *
William W. Helman (16)...........................................................   1,193,510          8.7          7.1
James Mortensen (17).............................................................      10,138            *            *
Timothy F. S. Cobb (18)..........................................................     503,065          3.7          3.0
All directors and executive officers as a group (10 persons) (19)................   7,189,057         51.4%        42.3%
</TABLE>
 
- -----------------------
 
*   Less than 1.0%
 
                                       54
<PAGE>
(1) Of the 4,380,559 shares of common stock owned by NPD, 601,838 shares of
    common stock are required to be sold to certain officers of NPD upon the
    exercise of options granted by NPD on these shares pursuant to an NPD
    employee plan. These options vest and become fully exercisable upon the
    consummation of this offering.
 
(2) Greylock IX Limited Partnership has expressed a desire to purchase shares of
    our common stock in this offering for $833,000. To the extent that Greylock
    IX Limited Partnership purchases such shares at a price of $17.00 per share,
    it will beneficially own approximately 1,242,510 shares, or 7.4% of our
    common stock after this offering. The partnership's address is One Federal
    Street, Boston, Massachusetts 02110.
 
(3) The address of The 1995 Scott Johnson Trust is c/o Franklin Green, Esq.,
    Trustee, Fried, Frank, Harris Shriver & Jacobson, One New York Plaza, New
    York, New York 10004-1980.
 
(4) The address of The 1995 Stacey Johnson Trust is c/o Franklin Green, Esq.,
    Trustee, Fried, Frank, Harris Shriver & Jacobson, One New York Plaza, New
    York, New York 10004-1980.
 
(5) Consists of 796,208 shares of common stock and warrants to purchase 133,417
    shares of common stock held by Whitney Equity Partners, L.P. and warrants to
    purchase 7,777 shares of common stock held by J. H. Whitney & Co. Each
    partnership may be deemed to beneficially own each other's shares because
    the general partners of each partnership are affiliated. Each partnership
    disclaims beneficial ownership of the other's shares. The partnerships'
    addresses are c/o J. H. Whitney & Co., 177 Broad Street, Stamford,
    Connecticut 06901.
 
(6) Consists of 905,824 shares of common stock owned by Oak Investment Partners
    VI, Limited Partnership and 21,135 shares of common stock owned by Oak VI
    Affiliates Fund, Limited Partnership. Each partnership may be deemed to
    beneficially own each other's shares because the general partners of each
    partnership are affiliated. Each partnership disclaims beneficial ownership
    of the other's shares. Oak Investment Partners VI and Oak VI Affiliates Fund
    have expressed a desire to purchase shares of our common stock in this
    offering for $417,000. To the extent that Oak Investment Partners VI and Oak
    VI Affiliates Fund purchase such shares at a price of $17.00 per share, they
    will beneficially own an aggregate of 951,459 shares, or 5.7% of our common
    stock after this offering. The partnerships' addresses are One Gorham
    Island, Westport, Connecticut 06880.
 
(7) Consists of 523,195 shares of common stock owned by Venrock Associates II,
    L.P. and 392,631 shares of common stock owned by Venrock Associates. Each
    partnership may be deemed to beneficially own each other's shares because
    the general partners of each partnership are affiliated. Each partnership
    disclaims beneficial ownership of the other's shares. Venrock Associates II
    and Venrock Associates have expressed a desire to purchase shares of our
    common stock in this offering for $417,000. To the extent that Venrock
    Associates II and Venrock Associates purchase such shares at a price of
    $17.00 per share, they will beneficially own 940,326 shares, or 5.6% of our
    common stock after this offering. The partnerships' addresses are 30
    Rockefeller Plaza, Room 5508, New York, New York 10112.
 
(8) Consists of 4,380,559 shares of common stock owned by NPD of which Mr.
    Johnson is the principal stockholder and Chief Executive Officer. As such,
    Mr. Johnson may be deemed to be the beneficial owner of such shares. Of the
    4,380,559 shares of common stock owned by NPD, 601,838 shares of common
    stock are issuable to certain officers of NPD upon the exercise of options
    granted on such shares pursuant to an NPD employee plan. Such options vest
    and become fully exercisable upon the consummation of this offering. In
    addition, The 1995 Scott Johnson Trust and The 1995 Stacey Johnson Trust are
    trusts for the benefit of family members of Mr. Johnson. Mr. Johnson does
    not exercise either voting or dispositive power over the securities held by
    either trust and disclaims beneficial ownership of the shares held by the
    trusts.
 
                                       55
<PAGE>
(9) Consists of 49,574 shares of common stock issuable upon the exercise of
    options. Does not include 108,739 shares of common stock issuable upon the
    exercise of options not currently exercisable within 60 days of March 31,
    1999. See "Management--Stock Options."
 
(10) Consists of 49,574 shares of common stock issuable upon the exercise of
    options. Does not include 108,739 shares of common stock issuable upon the
    exercise of options not currently exercisable within 60 days of March 31,
    1999. See "Management--Stock Options."
 
(11) Consists of 47,565 shares of common stock issuable upon the exercise of
    options, 47,130 of which were granted pursuant to an NPD benefit plan and
    which give Mr. Lynch the right to purchase shares of our common stock held
    by NPD. Does not include 77,725 shares of common stock issuable upon the
    exercise of options not currently exercisable within 60 days of March 31,
    1999. See "Management--Stock Options."
 
(12) Consists of 7,393 shares of common stock issuable upon the exercise of
    options. Does not include 82,096 shares of common stock issuable upon the
    exercise of options not currently exercisable within 60 days of March 31,
    1999. See "Management--Stock Options."
 
(13) Consists of 394,315 shares of common stock owned by Mr. Levy and 108,889
    shares of common stock owned by the Jeffrey C. Levy 1996 Children's Trust.
    Mr. Levy may be deemed the beneficial owner of the shares held by the Levy
    Trust. Mr. Levy disclaims beneficial ownership of the shares held by the
    Levy Trust. Mr. Levy has granted the underwriters an option to purchase up
    to 100,000 shares to cover over-allotments. The purchase price for the
    shares will equal the initial public price of this offering minus the
    underwriting discounts. If this option is exercised in full, Mr. Levy will
    beneficially own 403,204 shares, or 2.4% of our common stock after this
    offering.
 
(14) Consists of 796,208 shares of common stock and warrants to purchase 133,417
    shares of common stock issuable upon the exercise of a warrant owned by
    Whitney Equity Partners, L.P. and warrants to purchase 7,777 shares of
    common stock owned by J.H. Whitney & Co. Mr. Brooks is a managing member of
    J. H. Whitney Equity Partners, L.L.C., the general partner of Whitney Equity
    Partners, L.P. which possesses investment and voting power with respect to
    all shares owned by Whitney Equity Partners, L.P. Mr. Brooks disclaims
    beneficial ownership of the shares of common stock owned by Whitney Equity
    Partners, L.P. other than the shares attributable to his proportionate
    interest. Mr. Brooks is also a general partner of J. H. Whitney & Co. and a
    managing member of Whitney General Partner, L.L.C., which is also a general
    partner of J. H. Whitney & Co. which possess investment and voting power
    with respect to all shares owned by J. H. Whitney & Co. Mr. Brooks disclaims
    beneficial ownership of the shares of common stock owned by J. H. Whitney &
    Co. other than the shares attributable to his proportionate interest. See
    footnote (5) above. Mr. Brooks' address is c/o J. H. Whitney & Co., 177
    Broad Street, Stamford, Connecticut 06901.
 
(15) Consists of 10,138 shares issuable upon the exercise of options, 9,703 of
    which were granted pursuant to an NPD benefit plan and which give Mr. Kry
    the right to purchase shares of our common stock held by NPD. Does not
    include 15,631 shares of common stock issuable upon the exercise of options
    not currently exercisable within 60 days of March 31, 1999.
 
(16) Consists of 1,193,510 shares of common stock owned by Greylock IX Limited
    Partnership. If Greylock IX Limited Partnership purchases shares of our
    common stock in this offering, Mr. Helman may be deemed to beneficially own
    1,242,510 shares, or 7.4% of our common stock after this offering. See
    footnote (2) above. Mr. Helman is a general partner of Greylock and possess
    investment and voting power with respect to all such shares. Mr. Helman
    disclaims beneficial ownership of the shares of common stock owned by
    Greylock other than the shares attributable to his proportionate partnership
    interest in that fund. Mr. Helman's address is c/o Greylock IX Limited
    Partnership, One Federal Street, Boston, Massachusetts 02110.
 
                                       56
<PAGE>
(17) Consists of 10,138 shares exercisable upon the exercise of options, 9,703
    of which were granted pursuant to an NPD benefit plan and which give Mr.
    Mortensen the right to purchase shares of our common stock held by NPD. Does
    not include 15,631 shares of common stock issuable upon the exercise of
    options not currently exercisable within 60 days of March 31, 1999.
 
(18) Consists of 350,620 shares of common stock, owned by Mr. Cobb, 43,556
    shares of common stock owned by Mr. Cobb's wife, Madelyn Adams Cobb, and
    108,889 shares of common stock owned by The Timothy Fitzgerald Stephenson
    Cobb 1996 Children's Trust. Mr. Cobb may be deemed the beneficial owner of
    the shares held by Madelyn Adams Cobb and the Cobb Trust. Mr. Cobb disclaims
    beneficial ownership of the shares held by Madelyn Adams Cobb and the Cobb
    Trust. Mr. Cobb has granted the underwriters an option to purchase up to
    100,000 shares to cover over-allotments. The purchase price for the shares
    will equal the initial public price of this offering minus the underwriting
    discounts. If this option is exercised in full, Mr. Cobb will beneficially
    own 403,065 shares, or 2.4% of our common stock after this offering.
 
(19) Consists of 315,576 shares issuable upon the exercise of options and
    warrants to purchase common stock of which 66,536 options were granted
    pursuant to an NPD benefit plan which gives the holders of such options the
    right to purchase shares of our common stock held by NPD. Does not include
    408,561 shares of common stock issuable upon the exercise of options not
    currently exercisable within 60 days of March 31, 1999. If Greylock IX
    Limited Partnership purchases shares in this offering, our directors and
    executive officers as a group will beneficially own 7,238,057 shares, or
    42.6% of our common stock after this offering. See footnote (2) and (16)
    above.
 
                                       57
<PAGE>
                          DESCRIPTION OF CAPITAL STOCK
 
    Upon the closing of this offering, and the filing of our restated
certificate of incorporation, our authorized capital stock will consist of
60,000,000 shares of common stock, $.01 par value, and 5,000,000 shares of
preferred stock, $.01 par value.
 
    As of March 31, 1999, we had 13,727,828 shares of common stock outstanding
held by approximately 128 stockholders of record, and 41,446 shares of
redeemable preferred stock outstanding held by one stockholder of record. Upon
the closing of this offering, and after giving effect to the issuance of
3,000,000 shares of common stock in this offering, there will be 16,727,828
shares of common stock and no shares of preferred stock issued and outstanding.
See "--Preferred Stock."
 
COMMON STOCK
 
    Subject to preferences that may be applicable to any preferred stock
outstanding at the time, holders of our common stock are entitled to receive
dividends at times and in amounts as the board may determine. The holders of our
common stock have one vote for each share they hold on all matters submitted to
a vote of the stockholders. The holders of a majority of the shares of common
stock voted can elect all of the directors nominated for election. The holders
of our common stock are not entitled to preemptive rights and our common stock
is not subject to conversion or redemption. Upon a liquidation, dissolution or
winding-up, we will distribute pro rata to the holders of our common stock our
remaining assets, after payment of liquidation preferences, if any, on any
outstanding shares of preferred stock and payment of claims of creditors. Each
outstanding share of our common stock is, and all shares of our common stock
being purchased in this offering will be, duly and validly issued, fully paid
and nonassessable.
 
    There is currently no active trading market for our common stock. Our common
stock has been approved for quotation on the Nasdaq National Market under the
symbol "MMXI." See "Risk Factors--There may be volatility in our stock price."
 
PREFERRED STOCK
 
    Upon the closing of this offering, we will not have any shares of our
preferred stock outstanding. The 5,000,000 authorized shares of preferred stock
may by issued in one or more series without further stockholder action. The
board is authorized to determine the terms, limitations and relative rights and
preferences of the preferred stock, to establish series of preferred stock and
to determine the variations among series. If we issue preferred stock, it would
have priority over our common stock with respect to dividends and to other
distributions, including the distribution of assets upon liquidation. In
addition, we may be obligated to repurchase or redeem it. The board can issue
preferred stock without the approval of the holders of our common stock. The
holders of preferred stock may have voting and conversion rights, including
multiple voting rights, which could adversely affect the rights of the holders
of our common stock. We do not have any present plans to issue any shares of
preferred stock.
 
    REDEEMABLE PREFERRED STOCK
 
    As of the date of this prospectus, there are 41,446 shares of our redeemable
preferred stock issued and outstanding and held of record and beneficially by
NPD.
 
    The shares of redeemable preferred stock are entitled to accrued cumulative
dividends at a rate of 7% yearly, compounded quarterly, and payable when and as
declared by the board. If there is a liquidation, dissolution or winding up, the
holders of our redeemable preferred stock are entitled to be paid $100.00 per
share plus any accrued and unpaid dividends on our redeemable preferred stock
out of our available assets, before any payment may be made to the holders of
our common stock.
 
                                       58
<PAGE>
    Each holder of a share of redeemable preferred stock is entitled to 100
votes for each share held at each meeting of our stockholders with respect to
any and all matters presented to our stockholders for their consideration. The
holders of the redeemable preferred stock and the holders of the common stock
vote together as a single class, except as provided by law.
 
    We are required to redeem all outstanding shares of redeemable preferred
stock at a price equal to $100 per share plus all accrued and unpaid dividends
on each share if we close a public offering generating proceeds of at least $15
million.
 
WARRANTS
 
    As of March 31, 1999, we had outstanding warrants to purchase an aggregate
of 469,413 shares of common stock at a weighted average exercise price of $1.87.
Of these, warrants to purchase 337,272 shares of our common stock will expire
upon this offering, unless exercised earlier. In addition, warrants to purchase
132,141 shares of our common stock contain restrictions on transfer. These
warrants and any shares issued on their exercise may not be sold or transferred
unless the holder of the warrant first gives us and NPD the opportunity to
purchase the warrants or the underlying shares. Also, these warrants or the
underlying shares may not be transferred to any of our competitors. These
warrants contain anti-dilution provisions for stock splits and other
recapitalizations.
 
REGISTRATION RIGHTS
 
    Under an agreement between us and certain of our securities holders,
13,480,075 shares of common stock, referred to as registrable securities, are
entitled to rights with respect to the registration of the registrable
securities under the Securities Act commencing 180 days after this offering. If
we receive from the holders of more than 25% of the registrable securities a
written request to effect a registration with respect to all or a part of the
registrable securities, we must use our best efforts to effect such a
registration. We are only obligated to effect one of these registrations. The
holders of the registrable securities may choose to sell their securities
through an underwriter. However, any underwriter may limit the number of
registrable securities proposed to be included in that registration.
 
    When we are eligible to use a registration statement on Form S-3 to register
an offering of our securities, holders of more than 10% of the registrable
securities may request that we file a registration statement on Form S-3
covering all or a portion of the registrable securities held by them, provided
that the proceeds from that offering are at least $2.0 million.
 
    In addition, the holders of registrable securities have piggyback
registration rights. If we propose to register any of our common stock under the
Securities Act, other than pursuant to the registration rights noted above, the
holders of registrable securities may require us to include all or a portion of
their securities in each registration. However, the managing underwriter, if
any, of that offering has the right to limit the number of registrable
securities proposed to be included in that registration.
 
    We will bear all registration expenses incurred in connection with these
registrations. Each of the holders of registrable securities participating in
any registration would pay their own underwriting discounts, selling commissions
and stock transfer taxes applicable to the sale of their securities.
 
STOCKHOLDERS' AGREEMENT
 
    We and some of our stockholders entered into a stockholders' agreement. The
stockholders agreed to vote their shares of our voting capital stock so as to
cause the board to consist of eight persons. They also agreed to vote for the
election of five directors designated by our stockholders who held our
securities immediately prior to the closing of our merger with RelevantKnowledge
and the election of three directors designated by our stockholders who held
securities of RelevantKnowledge immediately prior to the closing of that merger.
In addition, the stockholders' agreement provides that we cannot
 
                                       59
<PAGE>
issue shares of any class of our capital stock or rights to acquire any shares
of our capital stock which issuance would decrease any party's outstanding
interest in the common stock, on a fully diluted basis, by greater than 5%,
without the approval of 75% of the board. The stockholders' agreement will
terminate upon the closing of this offering.
 
CO-SALE AGREEMENT
 
    Media Metrix, NPD, The 1995 Scott Johnson Trust, The 1995 Stacey Johnson
Trust and some of our other stockholders have entered into a co-sale agreement
restricting their transfer of our common stock. If NPD, The 1995 Scott Johnson
Trust or The 1995 Stacey Johnson Trust, collectively, the founders, want to sell
any of their shares of common stock, the other founders and the stockholders
party to the co-sale agreement have the right to include their shares of common
stock in that sale. The restrictions on transfer do not apply to transfers to
any other founder, to Tod Johnson or to a charity or charitable organization.
The co-sale agreement terminates upon the closing of this offering.
 
DELAWARE ANTI-TAKEOVER LAW AND CERTAIN CHARTER PROVISIONS
 
    Under Section 203 of the Delaware General Corporation Law, certain "business
combinations" between a Delaware corporation, whose stock generally is publicly
traded or held of record by more than 2,000 stockholders, and an "interested
stockholder" are prohibited for a three-year period following the date that such
stockholder became an interested stockholder, unless:
 
    - the corporation has elected in its certificate of incorporation or bylaws
      not to be governed by the Delaware anti-takeover law (we have not made
      such an election);
 
    - the business combination was approved by the board of the corporation
      before the other party to the business combination became an interested
      stockholder;
 
    - upon consummation of the transaction that made it an interested
      stockholder, the interested stockholder owned at least 85% of the voting
      stock of the corporation outstanding at the commencement of the
      transaction (excluding voting stock owned by directors who are also
      officers or held in employee stock plans in which the employees do not
      have a right to determine confidentially whether to tender or vote stock
      held by the plan); or
 
    - the business combination was approved by the board and ratified by 66 2/3%
      of the voting stock which the interested stockholder did not own.
 
    The three-year prohibition does not apply to certain business combinations
proposed by an interested stockholder following the announcement or notification
of certain extraordinary transactions involving the corporation and a person who
had not been an interested stockholder during the previous three years or who
became an interested stockholder with the approval of a majority of the
corporation's directors. The term "business combination" is defined generally to
include mergers or consolidations between a Delaware corporation and an
interested stockholder, transactions with an interested stockholder involving
the assets or stock of the corporation or its majority-owned subsidiaries and
transactions which increase an interested stockholder's percentage ownership of
stock. The term "interested stockholder" is defined generally as a stockholder
who becomes beneficial owner of 15% or more of a Delaware corporation's voting
stock. Section 203 could have the effect of delaying, deferring or preventing a
change in control of Media Metrix.
 
    In addition, provisions of our certificate of incorporation and bylaws which
will take effect upon the closing of this offering may have an anti-takeover
effect. They may delay, defer or prevent a tender offer or takeover attempt that
a stockholder might consider in its best interest, including those attempts that
might result in a premium over the market price for the shares held by our
stockholders. The following summarizes these provisions.
 
                                       60
<PAGE>
    CLASSIFIED BOARD OF DIRECTORS
 
    Our board will be divided into three classes of directors serving staggered
three-year terms. As a result, approximately one-third of our board will be
elected each year. These provisions, when coupled with the provision of our
certificate of incorporation authorizing the board to fill vacant directorships
or increase the size of the board, may deter a stockholder from removing
incumbent directors and simultaneously gaining control of the board.
 
    STOCKHOLDER ACTION; SPECIAL MEETING OF STOCKHOLDERS
 
    Our certificate of incorporation will provide that our stockholders may not
take action by written consent, but only at an annual or special meeting of
stockholders. Our bylaws will provide that special meetings of our stockholders
may be called only by the chairman of the board or a majority of the board.
 
    SUPERMAJORITY VOTING PROVISIONS
 
    Our certificate of incorporation will provide that the affirmative vote of
at least 66 2/3% of our stockholders is required to amend the provisions of our
certificate and bylaws relating to the classification of the board, stockholder
action by written consent and the calling of special meetings.
 
    AUTHORIZED BUT UNISSUED SHARES
 
    The authorized but unissued shares of common stock and preferred stock are
available for future issuance without stockholder approval. We may use these
shares for a variety of corporate purposes, including future public offerings to
raise additional capital, corporate acquisitions and employee benefit plans.
This could make it more difficult or discourage an attempt to obtain control of
us by means of a proxy contest, tender offer, merger or otherwise.
 
LIMITATION OF LIABILITY AND INDEMNIFICATION MATTERS
 
    We will enter into indemnification agreements with our current directors and
executive officers. These agreements and provisions of our certificate of
incorporation and bylaws may have the practical effect in some cases of
eliminating our stockholders' ability to collect monetary damages from our
directors. We believe that these contractual agreements and the provisions in
our certificate of incorporation and bylaws are necessary to attract and retain
qualified persons as directors and officers.
 
TRANSFER AGENT AND REGISTRAR
 
    The transfer agent and registrar for the common stock is Continental Stock
Transfer and Trust
Company.
 
                                       61
<PAGE>
                        SHARES ELIGIBLE FOR FUTURE SALE
 
    If our stockholders sell substantial amounts of our common stock, including
shares issued upon the exercise of outstanding options, in the public market
following this offering, the market price of our common stock could fall. These
sales also might make it more difficult for us to sell equity or equity-related
securities in the future and at a time and price that we deem appropriate.
 
    Upon completion of this offering, we will have outstanding an aggregate of
16,727,828 shares of our common stock, assuming no exercise of the underwriters'
over-allotment option and no exercise of outstanding options or warrants. As of
March 31, 1999, we had approximately 128 holders of our common stock. Of these
shares, all of the shares sold in this offering will be freely tradeable without
restriction or further registration under the Securities Act, unless such shares
are purchased by "affiliates" as that term is defined in Rule 144 under the
Securities Act. This leaves 13,727,828 shares eligible for sale in the public
market as follows:
 
<TABLE>
<CAPTION>
         NUMBER OF SHARES                                  DATE
- -----------------------------------  ------------------------------------------------
<C>                                  <S>
                --                   After the date of this prospectus.
 
             8,852,130               After 180 days from the date of this prospectus
                                     (subject, in some cases, to volume limitations).
 
             4,875,698               At various times after 180 days from the date of
                                     this prospectus.
</TABLE>
 
    LOCK-UP AGREEMENTS
 
    All of our officers and directors and substantially all of our stockholders
have signed lock-up agreements under which they agreed not to transfer or
dispose of, directly or indirectly, any shares of our common stock or any
securities convertible into or exercisable or exchangeable for shares of our
common stock, for a period of 180 days after the date of this prospectus.
Transfers or dispositions can be made sooner:
 
    - with the prior written consent of Donaldson, Lufkin & Jenrette Securities
      Corporation;
 
    - in the case of gifts or estate planning transfers where the donee signs a
      lock-up agreement; or
 
    - in the case of distributions to stockholders or affiliates of the
      stockholders where the recipient signs a lock-up agreement.
 
    RULE 144
 
    In general, under Rule 144 as currently in effect, beginning 90 days after
the date of this prospectus, a person who has beneficially owned shares of our
common stock for at least one year would be entitled to sell within any
three-month period a number of shares that does not exceed the greater of:
 
    - 1% of the number of shares of our common stock then outstanding, which
      will equal approximately 167,278 shares immediately after this offering;
      or
 
    - the average weekly trading volume of our common stock on the Nasdaq
      National Market during the four calendar weeks preceding the filing of a
      notice on Form 144 with respect to that sale.
 
    Sales under Rule 144 are also subject to manner of sale provisions and
notice requirements and to the availability of current public information about
us.
 
                                       62
<PAGE>
    RULE 144(K)
 
    Under Rule 144(k), a person who is not deemed to have been one of our
affiliates at any time during the 90 days preceding a sale, and who has
beneficially owned the shares proposed to be sold for at least two years,
including the holding period of any prior owner other than an affiliate, is
entitled to sell those shares without complying with the manner of sale, public
information, volume limitation or notice provisions of Rule 144. Therefore,
unless otherwise restricted, Rule 144(k) shares may be sold immediately upon the
completion of this offering.
 
    RULE 701
 
    In general, under Rule 701 of the Securities Act as currently in effect, any
of our employees, consultants or advisors who purchases shares of our common
stock from us in connection with a compensatory stock or option plan or other
written agreement is eligible to resell those shares 90 days after the effective
date of this offering in reliance on Rule 144, but without compliance with some
of the restrictions, including the holding period, contained in Rule 144.
 
    REGISTRATION RIGHTS
 
    After this offering, the holders of 13,480,075 shares of our common stock,
or their transferees, will be entitled to certain rights with respect to the
registration of those shares under the Securities Act. See "Description of
Capital Stock--Registration Rights." After this registration, these shares of
our common stock become freely tradeable without restriction under the
Securities Act. These sales could have a material adverse effect on the trading
price of our common stock.
 
    STOCK OPTIONS
 
    Immediately after this offering, we intend to file a registration statement
under the Securities Act covering 1,837,542 shares of common stock reserved for
issuance under our 1998 Equity Incentive Plan and our earlier Stock Option Plan
and the shares reserved for issuance upon exercise of outstanding non-plan
options. As of March 31, 1999, options to purchase 959,190 shares of common
stock were issued and outstanding. Upon the expiration of the lock-up agreements
describe above, at least 847,902 shares of common stock will be subject to
vested options, based on the number of options outstanding as of March 31, 1999.
This registration statement is expected to be filed and become effective as soon
as practicable after the effective date of this offering. Accordingly, shares of
our common stock registered under this registration statement will, subject to
vesting provisions and Rule 144 volume limitations applicable to our affiliates,
be available for sale in the open market immediately after the 180-day lock-up
agreements expire.
 
                                       63
<PAGE>
                                  UNDERWRITING
 
    Subject to the terms and conditions contained in an underwriting agreement
dated May 6, 1999, the underwriters named below, who are represented by
Donaldson, Lufkin & Jenrette Securities Corporation, BancBoston Robertson
Stephens Inc. and Thomas Weisel Partners LLC have severally agreed to purchase
from us the number of shares opposite their names below.
 
<TABLE>
<CAPTION>
                                                                    NUMBER
UNDERWRITERS:                                                      OF SHARES
<S>                                                                <C>
Donaldson, Lufkin & Jenrette Securities Corporation..............  1,130,000
BancBoston Robertson Stephens Inc................................    678,000
Thomas Weisel Partners LLC.......................................    452,000
ABN AMRO Incorporated............................................     40,000
Bear, Stearns & Co. Inc..........................................     40,000
BT Alex. Brown...................................................     40,000
CIBC World Markets Inc...........................................     40,000
Deutsche Bank Securities Inc.....................................     40,000
Hambrecht & Quist LLC............................................     40,000
ING Baring Furman Selz LLC.......................................     40,000
Lehman Brothers Inc..............................................     40,000
Merrill Lynch, Pierce, Fenner & Smith Incorporated...............     40,000
J.P. Morgan & Co.................................................     40,000
Morgan Stanley Dean Witter.......................................     40,000
Salomon Smith Barney.............................................     40,000
SG Cowen Securities Corporation..................................     40,000
William Blair & Company..........................................     20,000
Suntrust Equitable Securities....................................     20,000
First Union Capital Markets Corp.................................     20,000
Gerard Klauer Mattison & Co., LLC................................     20,000
Janney Montgomery Scott Inc......................................     20,000
Ladenburg Thalmann & Co. Inc.....................................     20,000
Legg Mason Wood Walker, Incorporated.............................     20,000
Morgan Keegan & Company, Incorporated............................     20,000
Raymond James & Associates, Inc..................................     20,000
Sands Brothers & Co., Ltd........................................     20,000
C.E. Unterberg, Towbin...........................................     20,000
                                                                   ---------
    Total........................................................  3,000,000
                                                                   ---------
                                                                   ---------
</TABLE>
 
    The underwriting agreement provides that the obligations of the several
underwriters to purchase and accept delivery of the shares included in this
offering are subject to approval, including the absence of any material adverse
change in our business and receipt of acceptable certificates, opinions and
letters from us, our counsel and the independent auditors. The underwriters are
obligated to purchase and accept delivery of all the shares, other than those
shares covered by the over-allotment option described below, if they purchase
any of the shares.
 
    The underwriters propose to initially offer some of the shares directly to
the public at the initial public offering price on the cover page of this
prospectus and some of the shares to certain dealers at the initial public
offering price less a concession not in excess of $0.71 per share. The
underwriters may allow, and such dealers may re-allow, a concession not in
excess of $0.10 per share on sales to other dealers. After the initial offering
of the shares to the public, the representatives may change the public
 
                                       64
<PAGE>
offering price and such concessions. The underwriters do not intend to confirm
sales to any accounts over which they exercise discretionary authority.
 
    The following table shows the underwriting fees to be paid to the
underwriters by us and the selling stockholders, and the offering expenses to be
paid by us, in connection with this offering. The underwriting fee is equal to
the public offering price per share of common stock less the amount paid by the
underwriters to us per share of common stock. Offering expenses, all of which we
will pay, are expenses incurred by us in connection with this offering and
include filing fees, Nasdaq listing fees, printing expenses and legal and
accounting expenses. These amounts are shown assuming both no exercise and full
exercise of the underwriters' option to purchase additional shares of our common
stock.
 
<TABLE>
<CAPTION>
                                                                           PAID BY SELLING
                                                 PAID BY MEDIA METRIX        STOCKHOLDERS
                                                ----------------------  ----------------------
                                                   NO         FULL         NO         FULL
                                                EXERCISE    EXERCISE    EXERCISE    EXERCISE
<S>                                             <C>        <C>          <C>        <C>
Underwriting fees per share...................  $    1.19   $    1.19          --   $    1.19
Total underwriting fees.......................  3,570,000   3,867,500          --     238,000
Offering expenses per share...................       0.33        0.31          --          --
Total offering expenses.......................  1,000,000   1,000,000          --          --
</TABLE>
 
    Thomas Weisel Partners LLC, one of the representatives of the underwriters,
was organized and registered as a broker-dealer in December 1998. Since December
1998, Thomas Weisel Partners has been named as a lead or co-manager on 20 filed
public offerings of equity securities, of which six have been completed, and has
acted as a syndicate member in an additional eight public offerings of equity
securities. Thomas Weisel Partners does not have any material relationship with
us or any of our officers, directors or other controlling persons, except with
respect to its contractual relationship with us pursuant to the underwriting
agreement entered into in connection with this offering.
 
    An electronic prospectus is available on the Web site maintained by
DLJDIRECT Inc., a selected dealer and an affiliate of Donaldson, Lufkin &
Jenrette Securities Corporation, and on the Web site of E*TRADE Securities,
Inc., a selected dealer. The underwriters have agreed to allocate a limited
number of shares to them for sale to their brokerage account holders. Other than
the prospectus in electronic format, the information on these Web sites relating
to this offering is not a part of this prospectus and has not been approved
and/or endorsed by us or any underwriter, and should not be relied on by
prospective investors.
 
    We and the selling stockholders have granted to the underwriters an option,
exercisable for 30 days after the date of this prospectus, to purchase up to
450,000 additional shares at the initial public offering price minus the
underwriting fees. The underwriters may exercise this option solely to cover
over-allotments, if any, made in connection with this offering. To the extent
that the underwriters exercise this option, each underwriter will become
obligated, subject to certain conditions, to purchase a number of additional
shares approximately proportionate to that underwriter's initial purchase
committment.
 
    We and the selling stockholders have agreed to indemnify the underwriters
against certain civil liabilities, including liabilities under the Securities
Act, or to contribute to payments that the underwriters may be required to make
in respect any of those liabilities.
 
    We, our executive officers and directors, and substantially all of our
stockholders have agreed, for a period of 180 days from the date of this
prospectus, not to, without the prior written consent of Donaldson, Lufkin &
Jenrette: (1) offer, pledge, sell, contract to sell, sell any option or contract
to purchase, purchase any option or contract to sell, grant any option, right or
warrant to purchase or otherwise transfer or dispose of, directly or indirectly,
any shares of our common stock or any securities
 
                                       65
<PAGE>
convertible into or exercisable or exchangeable for our common stock; or (2)
enter into any swap or other arrangement that transfer all or a portion of the
economic consequences associated with the ownership of any common stock,
regardless of whether any of the transactions described in clause (1) or (2) is
to be settled by the delivery of common stock, or such other securities, in cash
or otherwise. In addition, during this period, we have agreed not to file any
registration statement with respect to, and each of our executive officers and
directors and a significant majority of our stockholders have agreed not to make
any demand for, or exercise any right with respect to, the registration of any
shares of common stock or any securities convertible into or exercisable or
exchangeable for common stock (other than a registration statement registering
options or shares granted under a stock option plan) without the prior written
consent of Donaldson, Lufkin & Jenrette.
 
    At our request, the underwriters have reserved for sale at the initial
public offering price an aggregate of $2.5 million of shares of our common
stock, or approximately 147,059 shares based on the initial public offering
price of $17.00 per share, for sale to J.H. Whitney Value Fund I, L.P., Greylock
IX Limited Partnership, Venrock Associates II, L.P., Venrock Associates, Oak
Investment Partners VI, Limited Partnership and Oak VI Affiliates Fund, Limited
Partnership, all of whom are our stockholders. These stockholders have expressed
an interest in purchasing shares of our common stock in this offering. We cannot
assure you that any of the reserved shares will be purchased. The number of
shares available for sale to the general public in this offering will be reduced
by the number of reserved shares sold. Any reserved shares not so purchased will
be offered to the general public on the same basis as the other shares offered
in the offering.
 
    In addition, the underwriters, at our request, have reserved for sale at the
initial public offering price up to ten percent (10%) of the shares of common
stock to be sold in this offering for sale to our employees and other persons
designated by us. The number of shares available for sale to the general public
will be reduced to the extent that any reserved shares are purchased. Any
reserved shares not so purchased will be offered by the underwriters on the same
basis as the other shares offered hereby.
 
    Prior to this offering, there was no established trading market for our
common stock. The initial public offering price for the common stock in this
offering will be determined by negotiation among us and the representatives of
the underwriters. The factors to be considered in determining the initial public
offering price include the history of and the prospects for the industry in
which we compete, the ability of our management, our past and present
operations, our prospects for future earnings, the general condition of the
securities markets at the time of this offering and the recent market prices of
securities of generally comparable companies.
 
    Our common stock has been approved for quotation on the Nasdaq National
Market under the symbol "MMXI."
 
    Bayview Investors, Ltd., an entity affiliated with BancBoston Robertson
Stephens Inc., holds 63,039 shares of our common stock. In addition, Bayview
holds warrants to purchase 6,665 shares of our common stock at an exercise price
of $.03 per share.
 
    Other than in the United States, no action has been taken by us, the selling
stockholders or the underwriters that would permit a public offering of the
shares of our common stock included in this offering in any jurisdiction where
action for that purpose is required. The shares included in this offering may
not be offered or sold, directly or indirectly, nor may this prospectus or any
other offering material or advertisement in connection with the offer and sale
of any these shares be distributed or published in any jurisdiction, except
under circumstances that will result in compliance with the applicable rules and
regulations of that jurisdiction. Persons who receive this prospectus are
advised to inform themselves about and to observe any restrictions relating to
the offering of our common stock and the distribution of this prospectus. This
prospectus is not an offer to sell or a solicitation of an offer to buy any
shares of our common stock included in this offering in any jurisdiction where
that would not be permitted or legal.
 
                                       66
<PAGE>
    In connection with this offering, certain underwriters may engage in
transactions that stabilize, maintain or otherwise affect the price of our
common stock. Specifically, the underwriters may overallot this offering,
creating a syndicate short position. In addition, the underwriters may bid for
and purchase shares of our common stock in the open market to cover syndicate
short positions or to stabilize the price of our common stock. These activities
may stabilize or maintain the market price of our common stock above independent
market levels. The underwriters are not required to engage in these activities
and may end any of these activities at any time.
 
                                 LEGAL MATTERS
 
    The validity of the shares of common stock offered hereby will be passed
upon for Media Metrix by Fulbright & Jaworski L.L.P., New York, New York.
Certain legal matters in connection with the offering will be passed upon for
the underwriters by Brobeck, Phleger & Harrison LLP, New York, New York.
 
                                    EXPERTS
 
    Ernst & Young LLP, independent auditors, have audited our financial
statements at December 31, 1998 and 1997, and for each of the three years in the
period ended December 31, 1998, as set forth in their report. We have included
our financial statements in the prospectus and elsewhere in the registration
statement in reliance on Ernst & Young LLP's report, given on their authority as
experts in accounting and auditing.
 
    The balance sheets as of October 31, 1998 and December 31, 1997 and the
statements of operations, shareholders' equity and cash flows for the ten months
ended October 31, 1998, for the year ended December 31, 1997 and for the six
week period ended December 31, 1996, of RelevantKnowledge Inc. included in this
prospectus, have been included herein in reliance on the report of
PricewaterhouseCoopers LLP, independent accountants, given on the authority of
that firm as experts in accounting and auditing.
 
                   WHERE YOU CAN FIND ADDITIONAL INFORMATION
 
    We have filed with the commission a registration statement on Form S-1 with
respect to the common stock being sold in this offering. This prospectus
constitutes a part of that registration statement. This prospectus does not
contain all of the information set forth in the registration statement and the
exhibits and schedules to the registration statement, because some parts have
been omitted in accordance with rules and regulations of the commission. For
further information about us and our common stock being sold in this offering,
please refer to the registration statement and the exhibits and schedules filed
as a part of the registration statement. Statements contained in this prospectus
as to the contents of any contract, agreement or any other document referred to
are not necessarily complete; reference is made in each case to the copy of the
contract or document filed as an exhibit to the registration statement. Each
statement is qualified in all respects by reference to the exhibit. A copy of
the registration statement, including exhibits and schedules thereto, may be
inspected without charge and obtained at prescribed rates at the public
reference section of the commission at its principal offices, located at 450
Fifth Street, N.W., Washington, D.C. 20549, and may be inspected without charge
at the regional offices of the commission located at Seven World Trade Center,
13th Floor, New York, New York 10048, and Citicorp Center, 500 West Madison
Street, Suite 1400, Chicago, Illinois 60661. You may obtain information on the
operation of the Public Reference Room by calling the commission at
1-800-SEC-0330. The registration statement, including the exhibits and schedules
thereto, is also available at the commission's site on the Web at
http://www.sec.gov.
 
    We intend to furnish our stockholders annual reports containing financial
statements audited by our independent auditors and quarterly reports containing
unaudited financial information.
 
                                       67
<PAGE>
                         INDEX TO FINANCIAL STATEMENTS
 
<TABLE>
<CAPTION>
                                                                                                               PAGE
<S>                                                                                                          <C>
MEDIA METRIX, INC.
Report of Independent Auditors.............................................................................        F-2
Balance Sheets at December 31, 1997 and 1998 and March 31, 1999 (unaudited)................................        F-3
Statements of Operations for the years ended December 31, 1996, 1997 and 1998 and the three months ended
  March 31, 1998 and 1999 (unaudited)......................................................................        F-4
Statements of Stockholders' (Deficit) Equity for the years ended December 31, 1996, 1997 and 1998 and the
  three months ended March 31, 1999 (unaudited)............................................................        F-5
Statements of Cash Flows for the years ended December 31, 1996, 1997 and 1998 and the three months ended
  March 31, 1998 and 1999 (unaudited)......................................................................        F-6
Notes to Financial Statements..............................................................................        F-7
 
RELEVANTKNOWLEDGE, INC.
Report of Independent Accountants..........................................................................       F-19
Balance Sheets at December 31, 1997 and October 31, 1998...................................................       F-20
Statements of Operations for the six weeks ended December 31, 1996, the year ended December 31, 1997 and
  the ten months ended October 31, 1998....................................................................       F-21
Statements of Changes in Shareholders' Equity for the six weeks ended December 31, 1996, the year ended
  December 31, 1997 and the ten months ended October 31, 1998..............................................       F-22
Statements of Cash Flows for the six weeks ended December 31, 1996, the year ended December 31, 1997 and
  the ten months ended October 31, 1998....................................................................       F-23
Notes to Financial Statements..............................................................................       F-24
 
UNAUDITED PRO FORMA STATEMENT OF OPERATIONS
Statement of Operations for the year ended December 31, 1998...............................................       F-31
Notes to Unaudited Pro Forma Statement of Operations.......................................................       F-32
</TABLE>
 
                                      F-1
<PAGE>
                         REPORT OF INDEPENDENT AUDITORS
 
The Board of Directors
Media Metrix, Inc.
 
    We have audited the accompanying balance sheets of Media Metrix, Inc. as of
December 31, 1998 and 1997, and the related statements of operations,
stockholders' (deficit) equity, and cash flows for each of the three years in
the period ended December 31, 1998. These financial statements are the
responsibility of the Company's management. Our responsibility is to express an
opinion on these financial statements based on our audits.
 
    We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also includes
assessing the accounting principles used and significant estimates made by
management, as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.
 
    In our opinion, the financial statements referred to above present fairly,
in all material respects, the financial position of Media Metrix, Inc. at
December 31, 1998 and 1997, and the results of its operations and its cash flows
for each of the three years in the period ended December 31, 1998, in conformity
with generally accepted accounting principles.
 
                                          /s/ Ernst & Young LLP
 
New York, New York
February 22, 1999, except
 
  for the first paragraph of
  Note 1--Organization
  as to which the
  date is May 5, 1999
 
                                      F-2
<PAGE>
                               MEDIA METRIX, INC.
                                 BALANCE SHEETS
 
<TABLE>
<CAPTION>
                                                                                 DECEMBER 31,
                                                                            -----------------------
                                                                               1997        1998       MARCH 31,
                                                                                                        1999
                                                                                                     (UNAUDITED)
<S>                                                                         <C>         <C>          <C>
ASSETS
Current assets:
  Cash and cash equivalents...............................................  $1,869,013  $ 8,012,020  $ 2,385,260
  Receivables:
    Trade, less allowance for doubtful accounts of $100,000 in 1997,
      $220,000 in 1998 and $280,000 in 1999...............................     520,886    1,119,905    2,073,176
    Expenditures billable to clients......................................     219,877      250,432      287,017
                                                                            ----------  -----------  -----------
  Total receivables.......................................................     740,763    1,370,337    2,360,193
  Prepaid expenses and other current assets...............................      38,063      207,333      380,988
                                                                            ----------  -----------  -----------
Total current assets......................................................   2,647,839    9,589,690    5,126,441
 
Property and equipment, at cost, net of accumulated depreciation and
  amortization of $17,991 in 1997, $75,930 in 1998 and $140,931 in 1999...     116,834      649,790      636,823
Intangibles acquired, net of accumulated amortization of $479,000 in 1998
  and $1,227,600 in 1999..................................................      --        5,736,766    5,188,166
Other assets..............................................................      22,280       83,774      288,642
                                                                            ----------  -----------  -----------
Total assets..............................................................  $2,786,953  $16,060,020  $11,240,072
                                                                            ----------  -----------  -----------
                                                                            ----------  -----------  -----------
 
LIABILITIES AND STOCKHOLDERS' (DEFICIT) EQUITY
Current liabilities:
  Accounts payable and accrued liabilities................................  $  881,322  $ 2,308,323  $ 1,599,286
  Due to The NPD Group, Inc...............................................   1,284,315    4,705,825    1,338,955
  Advance billings to clients.............................................     529,220    1,391,275    1,743,097
  Current portion of long-term debt.......................................      --          127,179      133,184
                                                                            ----------  -----------  -----------
Total current liabilities.................................................   2,694,857    8,532,602    4,814,522
 
Long-term debt............................................................      --          225,353      190,173
Redeemable Preferred Stock--$1 par value; 41,446 shares authorized, issued
  and outstanding; liquidation and redemption value--$4,679,760 in 1998
  and $4,761,656 in 1999..................................................   4,366,022    4,679,760    4,761,656
Series A Convertible Preferred Stock--$1 par value; 495,603 shares
  authorized, issued and outstanding in 1997..............................   3,999,991      --           --
 
Commitments and contingencies
 
Stockholders' (deficit) equity:
  Preferred stock, $.01 par value--shares authorized: 4,462,951 in 1997
    and 4,958,554 in 1998 and 1999, none issued and outstanding...........      --          --           --
  Common stock, $.01 par value--60,000,000 shares authorized; shares
    issued and outstanding--6,523,330 in 1997, 13,098,808 in 1998 and
    13,727,828 in 1999....................................................      65,233      130,988      137,278
  Additional paid-in capital..............................................     281,656   18,149,203   21,352,553
  Common stock issuable...................................................      --        1,999,831      --
  Accumulated deficit.....................................................  (8,620,806) (16,093,242) (18,559,552)
  Deferred compensation...................................................      --       (1,564,475)  (1,456,558)
                                                                            ----------  -----------  -----------
Total stockholders' (deficit) equity......................................  (8,273,917)   2,622,305    1,473,721
                                                                            ----------  -----------  -----------
Total liabilities and stockholders' (deficit) equity......................  $2,786,953  $16,060,020  $11,240,072
                                                                            ----------  -----------  -----------
                                                                            ----------  -----------  -----------
</TABLE>
 
                            See accompanying notes.
 
                                      F-3
<PAGE>
                               MEDIA METRIX, INC.
 
                            STATEMENTS OF OPERATIONS
<TABLE>
<CAPTION>
                                                                                          THREE MONTHS ENDED
                                                          YEAR ENDED DECEMBER 31,              MARCH 31,
                                                     ----------------------------------  ---------------------
<S>                                                  <C>         <C>         <C>         <C>        <C>
                                                        1996        1997        1998       1998        1999
 
<CAPTION>
                                                                                              (UNAUDITED)
<S>                                                  <C>         <C>         <C>         <C>        <C>
Revenues...........................................  $1,032,629  $3,187,653  $6,330,485  $1,159,718 $3,177,539
Costs of revenues..................................   1,743,831   3,463,058   4,120,569    799,672   1,719,990
                                                     ----------  ----------  ----------  ---------  ----------
Gross profit (loss)................................    (711,202)   (275,405)  2,209,916    360,046   1,457,549
Operating expenses:
  Research and development.........................     587,731     865,498   1,382,375    248,167     680,891
  Sales and marketing..............................     928,993   2,021,409   2,888,195    575,118   1,334,546
  General and administrative.......................   1,147,768   1,516,396   3,084,255    434,195   1,157,227
  Amortization of intangibles......................          --          --     479,000         --     748,600
  Acquired in-process research and development.....          --          --   1,600,000         --          --
                                                     ----------  ----------  ----------  ---------  ----------
Total operating expenses...........................   2,664,492   4,403,303   9,433,825  1,257,480   3,921,264
                                                     ----------  ----------  ----------  ---------  ----------
Loss from operations...............................  (3,375,694) (4,678,708) (7,223,909)  (897,434) (2,463,715)
Interest income, net of interest expense of $11,374
  in 1998 and $16,692 in 1999......................          --      94,760      65,211     45,306      79,301
                                                     ----------  ----------  ----------  ---------  ----------
Net loss...........................................  (3,375,694) (4,583,948) (7,158,698)  (852,128) (2,384,414)
Preferred stock dividends..........................          --    (289,564)   (313,738)   (76,405)    (81,896)
                                                     ----------  ----------  ----------  ---------  ----------
Net loss applicable to common stockholders.........  $(3,375,694) $(4,873,512) $(7,472,436) $(928,533) $(2,466,310)
                                                     ----------  ----------  ----------  ---------  ----------
                                                     ----------  ----------  ----------  ---------  ----------
Basic and diluted net loss per share applicable to
  common stockholders..............................  $     (.52) $     (.75) $     (.98) $    (.14) $     (.19)
                                                     ----------  ----------  ----------  ---------  ----------
                                                     ----------  ----------  ----------  ---------  ----------
Shares used in the calculation of basic and diluted
  net loss per share applicable to common
  stockholders.....................................   6,523,330   6,523,330   7,618,511  6,523,330  13,296,447
                                                     ----------  ----------  ----------  ---------  ----------
                                                     ----------  ----------  ----------  ---------  ----------
</TABLE>
 
                            See accompanying notes.
 
                                      F-4
<PAGE>
                               MEDIA METRIX, INC.
 
                  STATEMENTS OF STOCKHOLDERS' (DEFICIT) EQUITY
 
                  YEARS ENDED DECEMBER 31, 1996, 1997 AND 1998
 
               AND THREE MONTHS ENDED MARCH 31, 1999 (UNAUDITED)
 
<TABLE>
<CAPTION>
                       OWNER'S/        COMMON STOCK      ADDITIONAL     COMMON                                      TOTAL
                       PARTNERS'   --------------------    PAID-IN      STOCK     ACCUMULATED     DEFERRED      STOCKHOLDERS'
                        CAPITAL      SHARES     AMOUNT     CAPITAL     ISSUABLE     DEFICIT     COMPENSATION   (DEFICIT) EQUITY
<S>                   <C>          <C>         <C>       <C>          <C>         <C>           <C>            <C>
Balance at January
  1, 1996,
  representing
  accumulated
  development costs
  contributed.......  $   371,600      --      $  --     $   --       $   --      $   (371,600)  $  --           $  --
Additional
  contributions by
  partners,
  including $573,000
  of accumulated
  development costs
  contributed.......      898,000      --         --         --           --           --           --               898,000
Net loss............      --           --         --         --           --        (3,375,694)     --            (3,375,694)
                      -----------  ----------  --------  -----------  ----------  ------------  ------------   ----------------
Balance at December
  31, 1996..........    1,269,600      --         --         --           --        (3,747,294)     --            (2,477,694)
Purchase of
  partnership
  interest..........    3,200,000      --         --         --           --           --           --             3,200,000
Exchange of
  partners' interest
  for 6,522,893
  shares of common
  stock and 41,446
  shares of
  Redeemable
  Preferred Stock...   (4,469,600)  6,522,893    65,229      259,771      --           --           --            (4,144,600)
Contribution of
  amounts owed to
  The NPD Group,
  Inc...............      --           --         --         380,977      --           --           --               380,977
Sale of common
  stock.............      --              437         4           96      --           --           --                   100
Costs incurred in
  connection with
  issuance of Series
  A Convertible
  Preferred Stock...      --           --         --        (359,188)     --           --           --              (359,188)
Payment of
  Redeemable
  Preferred Stock
  dividends.........      --           --         --         --           --           (68,142)     --               (68,142)
Accrual of
  Redeemable
  Preferred Stock
  dividends.........      --           --         --         --           --          (221,422)     --              (221,422)
Net loss............      --           --         --         --           --        (4,583,948)     --            (4,583,948)
                      -----------  ----------  --------  -----------  ----------  ------------  ------------   ----------------
Balance at December
  31, 1997..........                6,523,330    65,233      281,656      --        (8,620,806)     --            (8,273,917)
Conversion of Series
  A Convertible
  Preferred Stock...      --        2,155,176    21,552    3,978,439      --           --           --             3,999,991
Conversion of Series
  B Convertible
  Preferred Stock...      --          520,590     5,206    1,494,794      --           --           --             1,500,000
Issuance of common
  stock in
  connection with
  acquisition.......      --        3,890,825    38,908   10,461,092      --           --           --            10,500,000
Exercise of
  warrants..........      --            8,887        89          197      --           --           --                   286
Sale of common
  stock--194,380
  shares issuable...      --           --         --         --        1,999,831       --           --             1,999,831
Employee stock
  options...........      --           --         --       1,933,025      --           --       (1,933,025)         --
Amortization of
  deferred
  compensation......      --           --         --         --           --           --          368,550           368,550
Accrual of
  Redeemable
  Preferred Stock
  dividends.........      --           --         --         --           --          (313,738)     --              (313,738)
Net loss............      --           --         --         --           --        (7,158,698)     --            (7,158,698)
                      -----------  ----------  --------  -----------  ----------  ------------  ------------   ----------------
Balance at December
  31, 1998..........      --       13,098,808   130,988   18,149,203   1,999,831   (16,093,242) (1,564,475)        2,622,305
Issuance of common
  stock issuable
  (unaudited).......      --          194,380     1,944    1,997,887  (1,999,831)      --           --              --
Exercise of warrants
  and stock options
  (unaudited).......      --          434,640     4,346    1,205,463      --           --           --             1,209,809
Amortization of
  deferred
  compensation
  (unaudited).......      --           --         --         --           --           --          107,917           107,917
Accrual of
  Redeemable
  Preferred Stock
  dividends
  (unaudited).......      --           --         --         --           --           (81,896)     --               (81,896)
Net loss
  (unaudited).......      --           --         --         --           --        (2,384,414)     --            (2,384,414)
                      -----------  ----------  --------  -----------  ----------  ------------  ------------   ----------------
Balance at March 31,
  1999
  (unaudited).......  $   --       13,727,828  $137,278  $21,352,553  $   --      $(18,559,552) ($1,456,558)     $ 1,473,721
                      -----------  ----------  --------  -----------  ----------  ------------  ------------   ----------------
                      -----------  ----------  --------  -----------  ----------  ------------  ------------   ----------------
</TABLE>
 
                            See accompanying notes.
 
                                      F-5
<PAGE>
                               MEDIA METRIX, INC.
 
                            STATEMENTS OF CASH FLOWS
<TABLE>
<CAPTION>
                                                                                           THREE MONTHS ENDED
                                                          YEAR ENDED DECEMBER 31,              MARCH 31,
                                                     ----------------------------------  ----------------------
<S>                                                  <C>         <C>         <C>         <C>         <C>
                                                        1996        1997        1998        1998        1999
 
<CAPTION>
                                                                                              (UNAUDITED)
<S>                                                  <C>         <C>         <C>         <C>         <C>
OPERATING ACTIVITIES
Net loss...........................................  $(3,375,694) $(4,583,948) $(7,158,698) $ (852,128) $(2,384,414)
Adjustments to reconcile net loss to net cash used
  in operating activities:
  Contributed development costs....................     573,000          --          --          --          --
  Charge for acquired in-process research and
    development....................................          --          --   1,600,000          --          --
  Loss on disposal of equipment....................          --          --      13,174          --          --
  Provision for bad debts..........................          --     100,000     160,600          --      60,000
  Depreciation and amortization of property and
    equipment......................................          --      17,991      65,969       7,119      65,001
  Amortization of intangibles......................          --          --     479,000          --     748,600
  Amortization of deferred compensation............          --          --     368,550          --     107,917
  Changes in operating assets and liabilities:
    Receivables....................................    (629,704)   (211,059)   (427,652)   (230,616) (1,049,856)
    Prepaid expenses and other current assets......          --     (38,063)    (13,625)    (22,962)   (173,655)
    Other assets...................................          --     (22,280)     28,976          --       3,480
    Accounts payable and accrued liabilities.......      88,182     793,140     657,737    (388,019) (1,039,045)
    Advance billings to clients....................     220,020     309,200     393,581      63,745     351,822
    Due to The NPD Group, Inc......................   2,782,351  (1,117,059)  3,421,510     683,036  (3,366,870)
                                                     ----------  ----------  ----------  ----------  ----------
Net cash used in operating activities..............    (341,845) (4,752,078)   (410,878)   (739,825) (6,677,020)
 
INVESTING ACTIVITIES
Cash acquired......................................          --          --   3,185,112          --          --
Additions to property and equipment................          --    (134,825)   (117,489)     (6,418)    (52,034)
Proceeds from the sale of fixed assets.............          --          --       5,300          --          --
                                                     ----------  ----------  ----------  ----------  ----------
Net cash (used in) provided by investing
  activities.......................................          --    (134,825)  3,072,923      (6,418)    (52,034)
                                                     ----------  ----------  ----------  ----------  ----------
 
FINANCING ACTIVITIES
Proceeds from the exercise of warrants to purchase
  Series B Convertible Preferred Stock.............          --          --   1,500,000          --          --
Repayments on long-term debt.......................          --          --     (19,155)         --     (29,175)
Proceeds from sale of Series A Convertible
  Preferred Stock..................................          --   3,999,991          --          --          --
Payment of costs related to sale of Series A
  Convertible Preferred Stock......................          --    (359,188)         --          --          --
Partner contributions..............................     325,000   3,200,000          --          --          --
Proceeds from (repayment of) loan payable to
  affiliates.......................................     600,000    (600,000)         --          --          --
Proceeds from exercise of warrants and stock
  options..........................................          --          --         286          --   1,209,809
Payment of offering costs..........................          --          --          --          --     (78,340)
Payment of dividend................................          --     (68,142)         --          --          --
Sale of common stock...............................          --         100   1,999,831          --          --
                                                     ----------  ----------  ----------  ----------  ----------
Net cash provided by financing activities..........     925,000   6,172,761   3,480,962          --   1,102,294
                                                     ----------  ----------  ----------  ----------  ----------
Net increase (decrease) in cash and cash
  equivalents......................................     583,155   1,285,858   6,143,007    (746,243) (5,626,760)
Cash and cash equivalents at beginning of period...          --     583,155   1,869,013   1,869,013   8,012,020
                                                     ----------  ----------  ----------  ----------  ----------
Cash and cash equivalents at end of period.........  $  583,155  $1,869,013  $8,012,020  $1,122,770  $2,385,260
                                                     ----------  ----------  ----------  ----------  ----------
                                                     ----------  ----------  ----------  ----------  ----------
 
SUPPLEMENTAL INFORMATION
Interest paid......................................  $       --  $       --  $   11,374  $       --  $   16,692
                                                     ----------  ----------  ----------  ----------  ----------
                                                     ----------  ----------  ----------  ----------  ----------
</TABLE>
 
                            See accompanying notes.
 
                                      F-6
<PAGE>
                               Media Metrix, Inc.
 
                         Notes to Financial Statements
                               December 31, 1998
 
                   (Information as of March 31, 1999 and for
          the three months ended March 31, 1998 and 1999 is unaudited)
 
1. DESCRIPTION OF BUSINESS AND ORGANIZATION
 
DESCRIPTION OF BUSINESS
 
    Media Metrix, Inc., a Delaware Corporation ("Media Metrix"), provides
Internet audience measurement products and services to customers including media
companies, Internet advertisers and advertising agencies, technology companies
and financial institutions.
 
ORGANIZATION
 
    On October 15, 1998, Media Metrix stockholders approved a 2.96873-for-one
split of the outstanding shares of common stock which was effectuated as a stock
dividend, and on November 2, 1998, Media Metrix filed an amended and restated
certificate of incorporation increasing the number of authorized shares of
common stock from 10,000,000 to 15,000,000. On April 22, 1999, the Board of
Directors approved a 1.4648-for-one split of the outstanding shares of common
stock payable to stockholders of record on May 5, 1999. Also on April 22, 1999,
the Board of Directors and the stockholders approved an increase in the number
of authorized shares of common stock to 60,000,000, which became effective May
5, 1999. Retroactive effect has been given to these stock splits. All common
share, option and warrant data has been restated to reflect the stock splits.
 
    Media Metrix's business was originally conducted as a division within The
NPD Group, Inc. ("NPD") until March 1996, when PC Meter, L.P., a Delaware
limited partnership, ("PC Meter") (Media Metrix's predecessor) was formed to
conduct Media Metrix's business.
 
    On April 14, 1997, PC Meter was merged into Media Metrix. NPD originally
held 100,000 Class A Limited Partnership Units and 79,000 Class B Limited
Partnership Units of PC Meter. Two family trusts previously established for the
benefit of heirs to the sole shareholder of NPD (the "Family Trusts") each held
19,323.5 Class B Limited Partnership Units. In addition, PC Meter was indebted
to NPD in the amount of $3,951,029. On April 14, 1997, PC Meter was merged with
and into Media Metrix. Immediately prior to the merger, NPD purchased additional
Class A Limited Partnership Units for a purchase price of $3,200,000. Pursuant
to the terms of the Agreement and Plan of Merger between Media Metrix and PC
Meter, the Class A Limited Partnership Units were exchanged for a total of
41,446 shares of Media Metrix Redeemable Preferred Stock. The Class B Limited
Partnership Units were exchanged for a total of 6,522,893 shares of Media Metrix
common stock. Post-merger, Media Metrix repaid the amounts owed to NPD by PC
Meter. Of the amounts owed NPD, $3,570,052 was paid in cash and $380,977 was
forgiven.
 
    The above transactions were accounted for in a manner similar to that of a
"pooling of interests" in that the assets and liabilities and related revenues
and expenses of PC Meter have been reflected in the accompanying financial
statements at their historical book values.
 
2. SIGNIFICANT ACCOUNTING POLICIES
 
INTERIM FINANCIAL STATEMENTS
 
    The financial statements as of March 31, 1999 and for the three months ended
March 31, 1998 and 1999 have been prepared by Media Metrix without audit. In the
opinion of management, all adjustments (which include only normal recurring
adjustments) necessary to present fairly the financial position as of March 31,
1999 and the results of operations and cash flows for the three months ended
 
                                      F-7
<PAGE>
                               MEDIA METRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                   (INFORMATION AS OF MARCH 31, 1999 AND FOR
          THE THREE MONTHS ENDED MARCH 31, 1998 AND 1999 IS UNAUDITED)
 
2. SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
March 31, 1998 and 1999 have been made. Certain information and footnote
disclosures normally included in financial statements prepared in accordance
with generally accepted accounting principles have been condensed or eliminated.
 
    The results of operations for the three months ended March 31, 1999 are not
necessarily indicative of the results to be expected for any future interim
period or for the year ending December 31, 1999.
 
CASH AND CASH EQUIVALENTS
 
    Cash equivalents consist of highly liquid investments with a maturity date
of three months or less when purchased. Substantially all cash and cash
equivalents are held in one financial institution at December 31, 1998 and 1997.
Media Metrix's cash is exposed to risk to the extent the balance of the cash
accounts exceeds federally insured limits.
 
ACCOUNTING ESTIMATES
 
    The preparation of financial statements in conformity with generally
accepted accounting principles requires management to make estimates and
assumptions that affect the financial statements and accompanying notes. Actual
results could differ from those estimates.
 
REVENUE RECOGNITION
 
    Syndicated (recurring) products and services are sold on a subscription
basis. Revenues for such products and services are recognized over the term of
the related contract as products or services are provided. Buyers of syndicated
products and services typically are billed in advance for the next three months.
Billings rendered in advance of products or services being provided are recorded
as "Advance billings to clients" in the accompanying balance sheet.
 
    Revenues for customized (nonrecurring) products and services are recognized
in the period in which the products or services are provided.
 
PANEL COSTS
 
    Costs of establishing and maintaining a panel (a group of consumers who
furnish marketing data) are expensed in the year incurred and are included in
costs of revenues.
 
RESEARCH AND DEVELOPMENT COSTS
 
    Research and development costs primarily consist of costs attributable to
the development of new products and are expensed as incurred.
 
STOCK-BASED COMPENSATION
 
    Media Metrix accounts for its stock-based employee compensation agreements
in accordance with the provisions of Accounting Principles Board Opinion No. 25,
ACCOUNTING FOR STOCK ISSUED TO EMPLOYEES, and complies with the disclosure
provisions of Statement of Financial Accounting Standards No. 123, ACCOUNTING
FOR STOCK BASED COMPENSATION ("SFAS 123").
 
                                      F-8
<PAGE>
                               MEDIA METRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                   (INFORMATION AS OF MARCH 31, 1999 AND FOR
          THE THREE MONTHS ENDED MARCH 31, 1998 AND 1999 IS UNAUDITED)
 
2. SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
CONCENTRATIONS OF CREDIT RISK
 
    Media Metrix's policy is to review a customer's financial condition prior to
extending credit and, generally, collateral is not required. Credit losses are
provided for in the financial statements and have been within management's
expectations. Under the terms of certain contracts with its customers, Media
Metrix receives partial payments as the services are provided. One customer
accounted for approximately 19% of revenues for the year ended December 31,
1997.
 
DEPRECIATION AND AMORTIZATION
 
    Depreciation is provided over the estimated useful lives (3 to 7 years) of
the assets under the straight-line method. Leasehold improvements are amortized
on a straight-line basis over the shorter of the lease term or the estimated
useful life of the asset.
 
    Intangibles acquired are being amortized by the straight-line method over
one to three years from the date of acquisition (see Note 4).
 
LONG-LIVED ASSETS
 
    Media Metrix periodically reviews the carrying value of its long-lived
assets in determining the ultimate recoverability of their unamortized values
using future undiscounted cash flow analyses. Such a review has been performed
by management and does not indicate an impairment of such assets.
 
3. BASIC AND DILUTED NET LOSS PER SHARE
 
    Media Metrix computes net loss per share in accordance with the provisions
of Statement of Financial Accounting Standards No. 128, EARNINGS PER SHARE
("SFAS 128"), and SEC Staff Accounting Bulletin No. 98 ("SAB 98"). Under the
provisions of SFAS 128 and SAB 98, basic and diluted net loss per share
applicable to common stockholders is computed by dividing the net loss
applicable to common stockholders for the period by the weighted average number
of common shares outstanding for the period. The calculation of diluted net loss
per share excludes shares of common stock issuable upon exercise of employee
stock options and warrants (see Note 10), and the conversion of preferred stock
(see Note 8) as the effect of such exercises would be antidilutive.
 
                                      F-9
<PAGE>
                               MEDIA METRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                   (INFORMATION AS OF MARCH 31, 1999 AND FOR
          THE THREE MONTHS ENDED MARCH 31, 1998 AND 1999 IS UNAUDITED)
 
3. BASIC AND DILUTED NET LOSS PER SHARE (CONTINUED)
    The following sets forth the computation of basic and diluted net loss per
share:
 
<TABLE>
<CAPTION>
                                                                                     THREE MONTHS ENDED MARCH 31,
                                                  YEAR ENDED DECEMBER 31,
                                        -------------------------------------------  ----------------------------
<S>                                     <C>            <C>            <C>            <C>            <C>
                                            1996           1997           1998           1998           1999
Numerator:
  Net loss............................  $  (3,375,694) $  (4,583,948) $  (7,158,698) $    (852,128) $  (2,384,414)
  Preferred stock dividends...........       --             (289,564)      (313,738)       (76,405)       (81,896)
                                        -------------  -------------  -------------  -------------  -------------
  Net loss applicable to common
    stockholders......................  $  (3,375,694) $  (4,873,512) $  (7,472,436) $    (928,533) $  (2,466,310)
                                        -------------  -------------  -------------  -------------  -------------
                                        -------------  -------------  -------------  -------------  -------------
Denominator for basic and diluted loss
  per share--weighted average
  shares..............................      6,523,330      6,523,330      7,618,511      6,523,330     13,296,447
                                        -------------  -------------  -------------  -------------  -------------
                                        -------------  -------------  -------------  -------------  -------------
Basic and diluted loss per share
  applicable to common stockholders...  $        (.52) $        (.75) $        (.98) $        (.14) $        (.19)
                                        -------------  -------------  -------------  -------------  -------------
                                        -------------  -------------  -------------  -------------  -------------
</TABLE>
 
4. ACQUISITION
 
    On November 5, 1998, Media Metrix and an unrelated entity,
RelevantKnowledge, Inc. ("RKI") entered into an agreement and plan of
reorganization whereby RKI was merged into Media Metrix. The stockholders of RKI
exchanged all outstanding preferred and common stock of RKI for 3,890,825 newly
issued shares of common stock in Media Metrix. The fair value of the Media
Metrix common stock issued to the previous stockholders and option and warrant
holders of RKI is approximately $10,500,000. The purchase price was allocated as
follows: (i) net operating assets acquired--$3,182,000, including cash of
$3,185,000, (ii) acquired in-process research and development--$1,600,000, (iii)
debt--$372,000, and (iv) intangibles--$6,416,000, including related costs and
expenses of approximately $326,000.
 
    RKI had issued warrants to acquire shares of its common stock in connection
with prior sales of preferred and common stock and convertible secured
promissory notes. Such warrants were exchanged for warrants to purchase 360,907
shares of Media Metrix stock and are immediately exercisable as follows: 266,635
at $0.03 per share (8,887 of which were exercised in 1998 and 14,748 in 1999),
67,097 at $6.43 per share, 12,055 at $0.19 per share, 7,778 at $2.57 per share
and 7,342 at $5.14 per share. The warrants expire between April 2002 and May
2008. In addition, RKI had issued options to purchase shares of its common stock
to its employees pursuant to a stock option plan. Such options were exchanged
for options to purchase 46,775 shares of Media Metrix common stock at an
exercise price of $2.39 per share. All options are immediately exercisable and
expire from 2006 to 2008.
 
    Acquired in-process research and development represents the value attributed
to three technologies in development using the discounted value (using a 40%
discount rate) of the expected cash flow streams attributed to those items.
Adjustments, were made to the expected cash flow streams to incorporate
obsolescence of the technologies, the risk of similar technologies emerging in
the marketplace, and other factors that may reduce the value realized from the
in-process technologies. The three
 
                                      F-10
<PAGE>
                               MEDIA METRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                   (INFORMATION AS OF MARCH 31, 1999 AND FOR
          THE THREE MONTHS ENDED MARCH 31, 1998 AND 1999 IS UNAUDITED)
 
4. ACQUISITION (CONTINUED)
technologies relate to a data warehousing application (valued at $800,000), a
panel management tool (valued at $770,000), and an automated tracking system
(valued at $30,000). As of the acquisition date, the aforementioned technologies
are 25% to 50% complete and are expected to be completed in 1999.
 
    The estimates used by Media Metrix in valuing in-process research and
development were based on assumptions management believes to be reasonable but
which are inherently uncertain and unpredictable. Media Metrix's assumptions may
be incomplete or inaccurate, and no assurance can be given that unanticipated
events and circumstances will not occur. Accordingly, actual results may vary
from projected results.
 
    The above acquisition has been accounted for using the purchase method of
accounting and the operations of RKI have been included in the accompanying
financial statements from the date of acquisition.
 
    The following table reflects unaudited pro forma results of operations of
Media Metrix and RKI on the basis that the acquisition had taken place at the
beginning of the year for each of the periods presented:
 
<TABLE>
<CAPTION>
                                                                    YEAR ENDED DECEMBER 31
                                                                ------------------------------
<S>                                                             <C>             <C>
                                                                     1997            1998
Revenues......................................................  $    3,883,000  $    8,145,000
                                                                --------------  --------------
                                                                --------------  --------------
Net loss......................................................  $  (14,397,000) $  (15,898,000)
                                                                --------------  --------------
                                                                --------------  --------------
Net loss applicable to common stockholders....................  $  (14,686,000) $  (16,211,000)
                                                                --------------  --------------
                                                                --------------  --------------
Basic and diluted net loss per share applicable to common
  stockholders................................................  $        (1.41) $        (1.49)
                                                                --------------  --------------
                                                                --------------  --------------
Shares used in the calculation of basic and diluted net loss
  per share applicable to common stockholders.................      10,414,204      10,860,906
                                                                --------------  --------------
                                                                --------------  --------------
</TABLE>
 
    In management's opinion, the unaudited pro forma results of operations are
not indicative of the actual results that would have occurred had the
acquisition been consummated on January 1, 1997 or on January 1, 1998 or of
future operations of the combined companies under the management of Media
Metrix.
 
5. RELATED PARTY TRANSACTIONS
 
    Effective April 1, 1996 and as amended on September 30, 1998, NPD and Media
Metrix entered into a Management Services Agreement whereby NPD, among other
services, provides Media Metrix with computer processing capacity and certain
administrative functions. As compensation for the services, Media Metrix pays
NPD, on a monthly basis, an amount equal to (a) all expenses reasonably incurred
by NPD in performance of its duties under this agreement and (b) 105% of NPD's
overhead allocable to Media Metrix, as defined. The agreement may be terminated
by either party upon 90 days notice, provided NPD may not terminate prior to
March 31, 2002. Such charges pursuant to this agreement during the years ended
December 31, 1996, 1997 and 1998 and the three months ended March 31, 1998 and
1999, amounted to approximately $3,568,000, $5,831,000, $6,023,000, $1,848,000
 
                                      F-11
<PAGE>
                               MEDIA METRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                   (INFORMATION AS OF MARCH 31, 1999 AND FOR
          THE THREE MONTHS ENDED MARCH 31, 1998 AND 1999 IS UNAUDITED)
 
5. RELATED PARTY TRANSACTIONS (CONTINUED)
and $711,000, respectively. At December 31, 1997 and 1998 and March 31, 1999,
Media Metrix owed approximately $1,284,000, $4,706,000 and $1,339,000,
respectively, to NPD for such services. During the years ended December 31,
1996, 1997 and 1998 and the three months ended March 31, 1998 and 1999, weighted
average amounts owed by Media Metrix to NPD were approximately $1,546,000,
$1,492,000, $2,565,000, $1,654,000 and $2,003,000, respectively. Such amounts
are non-interest bearing.
 
    Media Metrix has entered into a Services Agreement with NPD as of September
30, 1998. Media Metrix has granted NPD access to its databases for any business
purpose of NPD which is not in direct competition with that of Media Metrix.
Media Metrix has also granted NPD a non-exclusive license to use certain
computer software owned by Media Metrix. Under the terms of the Services
Agreement, Media Metrix will receive a monthly fee of $2,500 plus expenses. The
Services Agreement is terminable by either party with 120 days notice.
 
    Media Metrix has entered into a License Agreement with NPD dated as of
November 5, 1998. NPD has granted to Media Metrix an exclusive, non-transferable
worldwide license to use certain NPD software. The fee is $11,000 per month
payable quarterly.
 
    In December 1996, Media Metrix entered into a short-term loan agreement with
NPD to borrow $600,000 to fund operations. In January 1997, Media Metrix repaid
the entire loan.
 
6. LONG-TERM DEBT
 
    In connection with the RKI acquisition (see Note 4), Media Metrix assumed
bank borrowings of approximately $372,000. The credit agreement provides for
borrowings up to $1,000,000. The balance outstanding at December 31, 1998 was
$352,532. The note bears interest at a rate of 20.27% per annum and is payable
in monthly principal and interest payments of $15,191.
 
                                      F-12
<PAGE>
                               MEDIA METRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                   (INFORMATION AS OF MARCH 31, 1999 AND FOR
          THE THREE MONTHS ENDED MARCH 31, 1998 AND 1999 IS UNAUDITED)
 
6. LONG-TERM DEBT (CONTINUED)
    Annual maturities of long-term debt are as follows:
 
<TABLE>
<S>                                                                 <C>
1999..............................................................  $ 127,179
2000..............................................................    152,955
2001..............................................................     72,398
                                                                    ---------
                                                                    $ 352,532
                                                                    ---------
                                                                    ---------
</TABLE>
 
7. ACCOUNTS PAYABLE AND ACCRUED LIABILITIES
 
    Accounts payable and accrued liabilities at December 31, 1997 and 1998 and
March 31, 1999 consist of:
 
<TABLE>
<CAPTION>
                                                           1997         1998          1999
<S>                                                     <C>         <C>           <C>
Trade accounts payable................................  $  359,000  $  1,079,000  $    467,000
Commissions and bonuses...............................     113,000       660,000       442,000
Panel costs...........................................     128,000        57,000        30,000
Other.................................................     281,000       512,000       660,000
                                                        ----------  ------------  ------------
                                                        $  881,000  $  2,308,000  $  1,599,000
                                                        ----------  ------------  ------------
                                                        ----------  ------------  ------------
</TABLE>
 
                                      F-13
<PAGE>
                               MEDIA METRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                   (INFORMATION AS OF MARCH 31, 1999 AND FOR
          THE THREE MONTHS ENDED MARCH 31, 1998 AND 1999 IS UNAUDITED)
 
8. PREFERRED STOCKS
 
    On April 14, 1997, Media Metrix issued: (i) 495,603 shares of its Series A
Convertible Preferred Stock ("Series A") and (ii) warrants to purchase 159,640
shares of its Series B Convertible Preferred Stock ("Series B") at an exercise
price of $12.53 per share through October 14, 1999, for proceeds of $3,999,991
pursuant to a private placement to three investors. Media Metrix incurred
approximately $359,000 of costs related to this private placement and issued an
investment advisor warrants to purchase 377,642 shares of Media Metrix's common
stock at an exercise price of $2.88 per share through October 14, 1999. The
value of such warrants was nominal. The investment advisor exercised warrants to
purchase 245,501 shares of common stock on March 31, 1999.
 
    Immediately prior to the RKI acquisition (see Note 4), the holders of the
Series A converted all issued and outstanding shares into 2,155,176 shares of
Media Metrix common stock. In addition, the holders of warrants to purchase
119,714 shares of Series B, exercised such warrants and immediately converted
the underlying Series B into 520,590 shares of Media Metrix common stock. The
remaining 39,926 warrants to purchase Series B were canceled and exchanged for
warrants to purchase 173,629 shares of Media Metrix common stock at an exercise
price of $2.88 per share. Such warrants were exercised on March 31, 1999. Media
Metrix amended and restated its certificate of incorporation to cancel the
Series A and Series B. Accordingly, at December 31, 1998, Media Metrix has
5,000,000 of authorized shares of undesignated preferred stock of which 41,446
has been designated to the Redeemable Preferred Stock.
 
    NPD owns 41,446 shares or 100% of the authorized, issued and outstanding
shares of Media Metrix's Redeemable Preferred Stock.
 
    The principal terms of the Redeemable Preferred Stock are as follows:
 
    - DIVIDENDS
 
      The holder of the Redeemable Preferred Stock is entitled to receive
      dividends at 7% per annum and shall accrue from the date of issuance
      whether or not declared. During April 1997, Media Metrix paid the holder
      of the Redeemable Preferred Stock dividends of approximately $68,000
      representing amounts accrued through April 1997. Cumulative but unpaid
      dividends on Redeemable Preferred Stock through December 31, 1998 are
      approximately $535,000.
 
    - LIQUIDATION PREFERENCE
 
      In the event of liquidation of Media Metrix, the holder of the Redeemable
      Preferred Stock is entitled to receive an amount equal to $100 per share
      ($4,144,600) plus any accrued but unpaid dividends.
 
    - REDEMPTION
 
      Upon the completion of a public offering of Media Metrix's common stock at
      a price per share of at least $3.45 and gross proceeds of at least
      $15,000,000 or certain other specified events as defined, Media Metrix is
      required to purchase the outstanding shares of Redeemable Preferred Stock
      at a price of $100 per share plus all accrued and unpaid dividends.
 
                                      F-14
<PAGE>
                               MEDIA METRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                   (INFORMATION AS OF MARCH 31, 1999 AND FOR
          THE THREE MONTHS ENDED MARCH 31, 1998 AND 1999 IS UNAUDITED)
 
8. PREFERRED STOCKS (CONTINUED)
    - VOTING RIGHTS
 
      The holder of the Redeemable Preferred Stock is entitled to 100 votes for
      each share held at any meeting of the stockholders of Media Metrix.
 
9. INCOME TAXES
 
    Since PC Meter was a limited partnership, no provision or benefit for
Federal or state income taxes was provided in the financial statements but the
income or loss was allocated directly to its partners. Beginning on April 14,
1997 when PC Meter was merged into Media Metrix, Media Metrix adopted the
provisions of Statement of Financial Accounting Standards No. 109, ACCOUNTING
FOR INCOME TAXES, in accounting for its income taxes. Accordingly, deferred tax
assets and liabilities are recognized for future tax consequences attributable
to differences between financial statement carrying amounts of existing assets
and liabilities and their respective tax bases. Deferred tax assets and
liabilities are measured using enacted rates expected to apply to taxable income
in the years in which those temporary differences are expected to be recovered
or settled. Significant components of Media Metrix's deferred tax assets are as
follows:
 
<TABLE>
<CAPTION>
                                                                          DECEMBER 31,
                                                                  ----------------------------
<S>                                                               <C>            <C>
                                                                      1997           1998
Deferred tax assets:
  Net operating loss carryforwards..............................  $     900,000  $   6,400,000
  Amounts payable to related party..............................        437,000      1,882,000
  Accounts receivable reserves..................................         34,000         88,000
                                                                  -------------  -------------
Total deferred tax assets.......................................      1,371,000      8,370,000
Valuation allowance for deferred tax assets.....................     (1,371,000)    (8,370,000)
                                                                  -------------  -------------
Net deferred taxes..............................................  $    --        $    --
                                                                  -------------  -------------
                                                                  -------------  -------------
</TABLE>
 
    At April 14, 1997, Media Metrix did not have any deferred tax assets or
liabilities and, accordingly, a valuation allowance for deferred tax assets was
not required. At the time of the RKI acquisition, RKI had deferred tax assets of
approximately $4,329,000 with an equal valuation allowance.
 
    As a result of losses from April 14, 1997 through December 31, 1998, Media
Metrix has available net operating loss carryforwards ("NOLs") of approximately
$16,000,000 for Federal income tax purposes that expire in 2012 and 2018.
Included in such amount are RKI pre-acquisition NOLs of approximately
$11,129,000 which expire through 2013. As a result of the RKI acquisition, under
Section 382 of the Internal Revenue Code, utilization of such NOLs will be
limited to approximately $600,000 per year over the next fifteen years. Future
benefits, if any, from the RKI NOLs would first reduce the intangibles acquired
and then income tax expense.
 
    In assessing the realizability of deferred tax assets, management considers
whether it is more likely than not that some portion or all of the deferred tax
assets will not be realized. The ultimate realization of deferred tax assets is
dependent upon the generation of future taxable income during the period in
which the NOLs can be utilized and the temporary differences become deductible.
Since Media
 
                                      F-15
<PAGE>
                               MEDIA METRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                   (INFORMATION AS OF MARCH 31, 1999 AND FOR
          THE THREE MONTHS ENDED MARCH 31, 1998 AND 1999 IS UNAUDITED)
 
9. INCOME TAXES (CONTINUED)
Metrix has incurred losses since inception, Media Metrix has established a
valuation allowance for deferred tax assets at December 31, 1998.
 
10. STOCK OPTIONS
 
    In November 1998, Media Metrix adopted the 1998 Equity Incentive Plan (the
"1998 Plan"). Under the 1998 Plan, Media Metrix may award incentive and other
non-statutory stock options, stock appreciation rights, restricted stock and
performance stock units and other stock units which are valued by reference to
the value of the common stock. Media Metrix also maintains the Media Metrix
Stock Option Plan ("Media Metrix Plan") which provides for the award of up to
519,222 shares of common stock in the form of incentive stock options and
non-statutory stock options. In February 1999, the Board of Directors, subject
to stockholder approval, adopted an amendment to increase the number of shares
under the 1998 Plan from 732,400 to 1,318,320.
 
    In October 1998, Media Metrix changed the provisions of all its outstanding
stock options granted prior to such time by removing the requirement of the
occurrence of an initial public offering before such options became exercisable.
This change resulted in a new measurement date. Accordingly, Media Metrix
established, as a separate component of stockholders' equity, deferred
compensation (approximately $724,000) equal to the number of options granted
times the difference in their exercise price and $2.30, the estimated fair value
of the common stock at the time of the new measurement date, and recorded
compensation expense in 1998 of approximately $348,000 representing the portion
of the deferred compensation which vested through December 31, 1998.
 
    On December 3, 1998, Media Metrix issued stock options to employees to
purchase 153,072 shares of common stock at $2.39 per share, which was considered
to be the fair value of the common stock at that time. Soon thereafter, Media
Metrix issued shares at $10.29 per share (see Note 12); accordingly, for
accounting purposes, Media Metrix used such per share value to record an
additional deferred compensation charge of $1,209,000 of which $20,150 was
amortized in December 1998.
 
                                      F-16
<PAGE>
                               MEDIA METRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                   (INFORMATION AS OF MARCH 31, 1999 AND FOR
          THE THREE MONTHS ENDED MARCH 31, 1998 AND 1999 IS UNAUDITED)
 
10. STOCK OPTIONS (CONTINUED)
    The following table summarizes activity in stock options:
<TABLE>
<CAPTION>
                                                                                                               THREE
                                                                                                               MONTHS
                                                      YEAR ENDED DECEMBER 31,                                  ENDED
                         ----------------------------------------------------------------------------------
<S>                      <C>        <C>              <C>        <C>              <C>        <C>              <C>
                                                                                                             MARCH 31,
                                    1996                        1997                        1998                1999
                         --------------------------  --------------------------  --------------------------  ----------
 
<CAPTION>
                          SHARES       WEIGHTED-      SHARES       WEIGHTED-      SHARES       WEIGHTED-       SHARES
                           UNDER        AVERAGE        UNDER        AVERAGE        UNDER        AVERAGE        UNDER
                          OPTION    EXERCISE PRICE    OPTION    EXERCISE PRICE    OPTION    EXERCISE PRICE     OPTION
<S>                      <C>        <C>              <C>        <C>              <C>        <C>              <C>
Balance, beginning of
  year.................     --         $  --           133,067     $    0.23       283,093     $    0.23        696,130
Grants.................    133,067          0.23       150,026          0.23       373,219          1.97        265,275
Exercises..............     --            --            --            --            --            --               (765)
Forfeitures............     --            --            --            --            (6,957)         2.30         (1,450)
Options issued in
  connection with
  acquisition..........     --            --            --            --            46,775          2.39             --
                         ---------                   ---------                   ---------                   ----------
Balance, end of year...    133,067          0.23       283,093          0.23       696,130          1.29        959,190
                         ---------                   ---------                   ---------                   ----------
                         ---------                   ---------                   ---------                   ----------
Weighted-average fair
  value of options
  issued during the
  period...............                $    0.07                   $    0.06                   $    3.42
 
<CAPTION>
 
<S>                      <C>
 
                           WEIGHTED-
                            AVERAGE
                           EXERCISE
                             PRICE
<S>                      <C>
Balance, beginning of
  year.................    $    1.29
Grants.................        11.26
Exercises..............         2.39
Forfeitures............         2.39
Options issued in
  connection with
  acquisition..........           --
 
Balance, end of year...         4.04
 
Weighted-average fair
  value of options
  issued during the
  period...............    $    2.79
</TABLE>
 
    The following tables summarize information about stock options outstanding
at December 31, 1998 and March 31, 1999:
 
<TABLE>
<CAPTION>
                            DECEMBER 31, 1998                             MARCH 31, 1999
                ------------------------------------------  ------------------------------------------
                                          WEIGHTED-AVERAGE                            WEIGHTED-AVERAGE
EXERCISE          OPTIONS      OPTIONS       REMAINING        OPTIONS      OPTIONS       REMAINING
PRICE           OUTSTANDING  EXERCISABLE  CONTRACTUAL LIFE  OUTSTANDING  EXERCISABLE  CONTRACTUAL LIFE
<S>             <C>          <C>          <C>               <C>          <C>          <C>
$ 0.23........     283,093       83,231        2.6 years       283,093       83,231        2.4 years
  0.35........      70,665           --              4.2        70,665       14,133              4.0
  2.30........     142,525           --              4.5       142,525           --              4.3
  2.39........     199,847       46,775              9.7       197,632       46,775              9.5
 11.26........          --           --               --       265,275           --              9.8
                -----------  -----------                    -----------  -----------
                   696,130      130,006              5.2       959,190      144,139              6.3
                -----------  -----------                    -----------  -----------
                -----------  -----------                    -----------  -----------
</TABLE>
 
    Media Metrix has reserved 3,639,448 and 2,306,213 shares of common stock for
issuance of all options and warrants at December 31, 1998 and March 31, 1999,
respectively.
 
FAIR VALUE DISCLOSURES
 
    Pro forma information regarding net loss and net loss per share is required
by SFAS 123, which also requires that the information be determined as if Media
Metrix has accounted for its stock options under the fair value method of that
statement. The fair value for these options was estimated using the minimum
value method with the following assumptions: no dividend yield, weighted-average
expected life of the option of 5 years, and risk-free interest rates of 6.6%,
6.0% and 5.7% for the years ended December 31, 1996, 1997 and 1998,
respectively.
 
                                      F-17
<PAGE>
                               MEDIA METRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                   (INFORMATION AS OF MARCH 31, 1999 AND FOR
          THE THREE MONTHS ENDED MARCH 31, 1998 AND 1999 IS UNAUDITED)
 
10. STOCK OPTIONS (CONTINUED)
    Because the determination of fair value of all options granted after such
time as Media Metrix becomes a public entity will include an expected volatility
factor in addition to the factors described above, the results presented below
may not be indicative of future periods.
 
    For purposes of pro forma disclosures, the estimated fair value of the
options is amortized to expense over the options' vesting period. Media Metrix's
pro forma financial information is as follows:
 
<TABLE>
<CAPTION>
                                                             YEAR ENDED DECEMBER 31,
                                                   -------------------------------------------
<S>                                                <C>            <C>            <C>
                                                       1996           1997           1998
Net loss applicable to common stockholders:
  As reported....................................  $  (3,375,694) $  (4,873,512) $  (7,472,436)
                                                   -------------  -------------  -------------
                                                   -------------  -------------  -------------
  Pro forma......................................  $  (3,376,754) $  (4,875,943) $  (7,487,969)
                                                   -------------  -------------  -------------
                                                   -------------  -------------  -------------
Net loss applicable to common stockholders per
share:
  As reported....................................  $        (.52) $        (.75) $        (.98)
                                                   -------------  -------------  -------------
                                                   -------------  -------------  -------------
  Pro forma......................................  $        (.52) $        (.75) $        (.98)
                                                   -------------  -------------  -------------
                                                   -------------  -------------  -------------
</TABLE>
 
11. LEASE COMMITMENTS
 
    Media Metrix leases office space in New York, California and Georgia. At
December 31, 1998, the future minimum lease payments under noncancellable
operating leases with initial or remaining lease terms in excess of one year are
as follows:
 
<TABLE>
<S>                                                                 <C>
Year ending December 31:
1999..............................................................  $ 391,000
2000..............................................................    223,000
2001..............................................................     81,000
2002..............................................................     58,000
2003..............................................................      5,000
                                                                    ---------
                                                                    $ 758,000
                                                                    ---------
                                                                    ---------
</TABLE>
 
    Rent expense approximated $39,000, $207,000 and $356,000 for the years ended
December 31, 1996, 1997 and 1998, respectively.
 
12. SUBSEQUENT EVENT
 
    On January 4, 1999, Media Metrix issued to a foreign investor 194,380 shares
of common stock at a purchase price per share of $10.29, for an aggregate
purchase price of approximately $2,000,000, pursuant to a stock purchase
agreement. Media Metrix had received the proceeds from this transaction on
December 31, 1998 and has recorded "common stock issuable" in the accompanying
balance sheet.
 
                                      F-18
<PAGE>
                       REPORT OF INDEPENDENT ACCOUNTANTS
 
To the Board of Directors and Shareholders of
RelevantKnowledge, Inc.
 
    In our opinion, the accompanying balance sheets and the related statements
of operations, of changes in shareholders' equity and of cash flows present
fairly, in all material respects, the financial position of RelevantKnowledge,
Inc. at October 31, 1998 and December 31, 1997, and the results of its
operations and its cash flows for the ten month period ended October 31, 1998,
for the year ended December 31, 1997 and for the six week period ended December
31, 1996, in conformity with generally accepted accounting principles. These
financial statements are the responsibility of the Company's management; our
responsibility is to express an opinion on these financial statements based on
our audits. We conducted our audits of these statements in accordance with
generally accepted auditing standards which require that we plan and perform the
audit to obtain reasonable assurance about whether the financial statements are
free of material misstatement. An audit includes examining, on a test basis,
evidence supporting the amounts and disclosures in the financial statements,
assessing the accounting principles used and significant estimates made by
management, and evaluating the overall financial statement presentation. We
believe that our audits provide a reasonable basis for the opinion expressed
above.
 
                                          /s/ PricewaterhouseCoopers LLP
 
Atlanta, Georgia
April 8, 1999
 
                                      F-19
<PAGE>
                            RELEVANTKNOWLEDGE, INC.
 
                                 BALANCE SHEETS
 
<TABLE>
<CAPTION>
                                                                                     DECEMBER 31,    OCTOBER 31,
                                                                                         1997            1998
<S>                                                                                  <C>            <C>
ASSETS
Current assets
  Cash and cash equivalents........................................................  $     998,827  $    2,963,218
  Accounts receivable..............................................................        213,575         292,038
  Unbilled work in progress........................................................       --                70,484
  Other current assets.............................................................        114,009          76,745
                                                                                     -------------  --------------
        Total current assets.......................................................      1,326,411       3,402,485
Fixed assets, net..................................................................        749,761         780,884
Other assets.......................................................................          4,983          98,803
                                                                                     -------------  --------------
        Total assets...............................................................  $   2,081,155  $    4,282,172
                                                                                     -------------  --------------
                                                                                     -------------  --------------
LIABILITIES AND SHAREHOLDERS' EQUITY
Current liabilities
  Accounts payable and accrued expenses............................................  $     619,552  $      402,950
  Commissions payable..............................................................       --               292,515
  Deferred revenue.................................................................        160,887         468,474
  Current portion of long-term debt................................................       --               123,326
                                                                                     -------------  --------------
        Total current liabilities..................................................        780,439       1,287,265
Long-term debt.....................................................................       --               248,361
                                                                                     -------------  --------------
        Total liabilities..........................................................        780,439       1,535,626
                                                                                     -------------  --------------
Commitments and contingencies
 
Shareholders' equity
  Common stock, no par value; 15,500,000 and 15,000,000 shares authorized at
    October 31, 1998 and December 31, 1997, respectively; 3,849,458 and 3,603,570
    shares issued and outstanding at October 31, 1998 and December 31, 1997,
    respectively...................................................................        210,183       1,317,471
  Series A-1 convertible preferred stock; 1,500,000 shares authorized; 1,456,949
    issued and outstanding at October 31, 1998 and December 31, 1997,
    respectively...................................................................        881,885         881,885
  Series B-1 convertible preferred stock; 3,000,000 shares authorized; 2,754,587
    shares issued and outstanding at October 31, 1998 and December 31, 1997,
    respectively...................................................................      4,223,575       4,221,619
  Series B-2 convertible preferred stock; 1,000,000 shares authorized; 858,420
    shares issued and outstanding at October 31, 1998 and December 31, 1997,
    respectively...................................................................      1,469,497       1,469,497
  Series C-1 convertible preferred stock; 3,500,000 shares authorized; 2,713,321
    and 0 shares issued and outstanding at October 31, 1998 and December 31 1997,
    respectively...................................................................       --             6,686,403
  Series C-2 convertible preferred stock; 1,000,000 shares authorized; no shares
    issued or outstanding at October 31, 1998 and December 31, 1997,
    respectively...................................................................       --              --
  Accumulated deficit..............................................................     (5,484,424)    (11,830,329)
                                                                                     -------------  --------------
        Total shareholders' equity.................................................      1,300,716       2,746,546
                                                                                     -------------  --------------
        Total liabilities and shareholders' equity.................................  $   2,081,155  $    4,282,172
                                                                                     -------------  --------------
                                                                                     -------------  --------------
</TABLE>
 
   The accompanying notes are an integral part of these financial statements.
 
                                      F-20
<PAGE>
                            RELEVANTKNOWLEDGE, INC.
 
                            STATEMENTS OF OPERATIONS
 
<TABLE>
<CAPTION>
                                                                        SIX WEEKS                    TEN MONTHS
                                                                          ENDED       YEAR ENDED        ENDED
                                                                       DECEMBER 31,  DECEMBER 31,    OCTOBER 31,
                                                                           1996          1997           1998
<S>                                                                    <C>           <C>            <C>
Revenues
  Information services...............................................   $   --       $     157,032  $   1,730,744
  Technology licensing and support...................................       --             537,879         83,486
  Other income.......................................................       --            --               95,909
                                                                       ------------  -------------  -------------
 
      Total revenues.................................................       --             694,911      1,910,139
 
Costs of sales.......................................................       --           2,510,621      2,879,037
Sales and marketing..................................................        8,912       1,433,173      1,623,500
General and administrative...........................................       30,732       1,440,551      2,973,230
Research and development.............................................      103,925         651,421        780,277
                                                                       ------------  -------------  -------------
      Total costs and expenses.......................................      143,569       6,035,766      8,256,044
                                                                       ------------  -------------  -------------
Net loss.............................................................   $ (143,569)  $  (5,340,855) $  (6,345,905)
                                                                       ------------  -------------  -------------
                                                                       ------------  -------------  -------------
</TABLE>
 
   The accompanying notes are an integral part of these financial statements.
 
                                      F-21
<PAGE>
                            RELEVANTKNOWLEDGE, INC.
 
                 STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY
 
<TABLE>
<CAPTION>
                                            COMMON STOCK             PREFERRED STOCK                           TOTAL
                                      ------------------------  -------------------------   ACCUMULATED    SHAREHOLDERS'
                                        SHARES       AMOUNT       SHARES       AMOUNT         DEFICIT         EQUITY
<S>                                   <C>         <C>           <C>         <C>            <C>             <C>
Balance, November 20, 1996..........      --           --           --           --              --             --
  Issuance of common stock..........   3,500,000  $      3,500                                             $       3,500
  Issuance of preferred stock.......                             1,181,310  $     750,000                        750,000
  Net loss..........................                                                       $     (143,569)      (143,569)
                                      ----------  ------------  ----------  -------------  --------------  -------------
Balance, December 31, 1996..........   3,500,000         3,500   1,181,310        750,000        (143,569)       609,931
  Issuance of preferred stock, net
    of offering costs...............                             3,888,646      5,824,957                      5,824,957
  Exercise of common stock
    warrants........................     103,570       169,998                                                   169,998
  Issuance of employee stock
    options.........................                    36,685                                                    36,685
  Net loss..........................                                                           (5,340,855)    (5,340,855)
                                      ----------  ------------  ----------  -------------  --------------  -------------
Balance, December 31, 1997..........   3,603,570       210,183   5,069,956      6,574,957      (5,484,424)     1,300,716
  Issuance of preferred stock, net
    of offering costs...............                             2,713,321      6,684,447                      6,684,447
  Issuance of common stock
    warrants........................                   970,740                                                   970,740
  Exercise of employee stock
    options.........................     245,888       136,548                                                   136,548
  Net loss..........................                                                           (6,345,905)    (6,345,905)
                                      ----------  ------------  ----------  -------------  --------------  -------------
Balance, October 31, 1998...........   3,849,458  $  1,317,471   7,783,277  $  13,259,404  $  (11,830,329) $   2,746,546
                                      ----------  ------------  ----------  -------------  --------------  -------------
                                      ----------  ------------  ----------  -------------  --------------  -------------
</TABLE>
 
   The accompanying notes are an integral part of these financial statements.
 
                                      F-22
<PAGE>
                            RELEVANTKNOWLEDGE, INC.
 
                            STATEMENTS OF CASH FLOWS
 
<TABLE>
<CAPTION>
                                                                        SIX WEEKS                    TEN MONTHS
                                                                          ENDED       YEAR ENDED        ENDED
                                                                       DECEMBER 31,  DECEMBER 31,    OCTOBER 31,
                                                                           1996          1997           1998
<S>                                                                    <C>           <C>            <C>
Cash flows from operating activities
  Net loss...........................................................   $ (143,569)  $  (5,340,855) $  (6,345,905)
    Adjustments to reconcile net loss to cash used in operating
      activities
      Depreciation and amortization..................................          368         103,173        143,589
      Expense recorded for issuance of warrants......................       --            --              970,740
      Expense recorded for issuance of employee stock options........       --              36,685       --
      Noncash interest expense.......................................       --            --               33,350
      Loss on disposal of fixed assets...............................       --            --               35,048
      Change in operating assets and liabilities:
        Accounts receivable..........................................       --            (213,575)       (78,463)
        Unbilled work in progress....................................       --            --              (70,484)
        Other current assets.........................................       --            (112,977)         4,418
        Other assets.................................................      (11,768)       --              (60,974)
        Accounts payable and accrued expenses........................       96,800         522,752       (216,602)
        Commissions payable..........................................       --            --              292,515
        Deferred revenue.............................................       --             160,887        307,587
                                                                       ------------  -------------  -------------
          Net cash used in operating activities......................      (58,169)     (4,843,910)    (4,985,181)
                                                                       ------------  -------------  -------------
  Cash flows from investing activities
    Proceeds from the sale of fixed assets...........................       --            --                6,500
    Purchases of fixed assets........................................      (21,042)       (826,507)      (216,260)
                                                                       ------------  -------------  -------------
          Net cash used in investing activities......................      (21,042)       (826,507)      (209,760)
                                                                       ------------  -------------  -------------
  Cash flows from financing activities
    Proceeds from issuance of common and preferred stock, net of
      offering costs.................................................      753,500       5,994,955      3,787,645
    Proceeds from issuance of convertible secured promissory notes
      and attached warrants..........................................       --            --            3,000,000
    Proceeds from long-term debt.....................................       --            --              480,722
    Payments on long-term debt.......................................       --            --             (109,035)
                                                                       ------------  -------------  -------------
          Net cash provided by financing activities..................      753,500       5,994,955      7,159,332
                                                                       ------------  -------------  -------------
  Net increase in cash and cash equivalents..........................      674,289         324,538      1,964,391
  Cash and cash equivalents at beginning of period...................       --             674,289        998,827
                                                                       ------------  -------------  -------------
  Cash and cash equivalents at end of period.........................   $  674,289   $     998,827  $   2,963,218
                                                                       ------------  -------------  -------------
                                                                       ------------  -------------  -------------
Supplemental cash flow disclosures
  Cash paid for interest.............................................   $   --       $    --        $      58,064
                                                                       ------------  -------------  -------------
                                                                       ------------  -------------  -------------
  Conversion of convertible secured promissory notes to Series C-1
    preferred stock..................................................   $   --       $    --        $   3,000,000
                                                                       ------------  -------------  -------------
                                                                       ------------  -------------  -------------
</TABLE>
 
   The accompanying notes are an integral part of these financial statements.
 
                                      F-23
<PAGE>
                            RELEVANTKNOWLEDGE, INC.
 
                         NOTES TO FINANCIAL STATEMENTS
 
1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
 
DESCRIPTION OF BUSINESS
 
    RelevantKnowledge, Inc. (the "Company") provides internet demographics, site
visit statistics, and additional usage-related information. The Company operates
in a single business segment.
 
CASH AND CASH EQUIVALENTS
 
    The Company considers all highly liquid investments with a maturity of three
months or less when purchased to be cash equivalents.
 
FIXED ASSETS
 
    Fixed assets are recorded at cost less accumulated depreciation, which is
computed using the straight-line method over the estimated useful lives of the
related assets; generally five to seven years. Upon sale, retirement or other
disposition of these assets, the cost and the related accumulated depreciation
are removed from the respective accounts and any gain or loss on the disposition
is included in operations.
 
    Leasehold improvements are amortized over the lesser of the useful life of
the improvement or the remaining lease term.
 
INCOME TAXES
 
    The Company accounts for income taxes using the provisions of Statement of
Financial Accounting Standards ("SFAS") No. 109, "Accounting for Income Taxes."
Under SFAS 109, deferred tax assets and liabilities are determined based on
differences between the financial reporting and tax basis of assets and
liabilities. Differences between the financial reporting and tax basis of assets
and liabilities at October 31, 1998 and December 31, 1997 are not significant.
 
    The Company has net operating loss carryforwards for Federal income tax
purposes of approximately $11,129,000 and $5,450,000 at October 31, 1998 and
December 31, 1997, respectively, that expire between 2011 and 2018. Such net
operating losses give rise to deferred tax assets of approximately $4,329,000
and $2,100,000 at October 31, 1998 and December 31, 1997, respectively. The
Company has recorded a valuation allowance equal to the amount of the deferred
tax assets at both October 31, 1998 and December 31, 1997, because it is deemed
more likely than not that such assets will not be realized.
 
USE OF ESTIMATES
 
    The preparation of financial statements in conformity with generally
accepted accounting principles requires management to make estimates and
assumptions that affect the reported amounts of assets and liabilities and
disclosure of contingent assets and liabilities at the date of the financial
statements and the reported amounts of revenue and expenses during the reporting
period. Actual results could differ from those estimates.
 
SOFTWARE DEVELOPMENT COSTS
 
    The Company capitalizes costs related to the development of certain software
products in accordance with SFAS 86 "Accounting For the Costs of Computer
Software to be Sold, Leased, or Otherwise Marketed" which requires
capitalization to begin when technological feasibility has been established
 
                                      F-24
<PAGE>
                            RELEVANTKNOWLEDGE, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
and ends when the product is available for general release to customers.
Software development costs incurred prior to technological feasibility are
considered research and development costs and are expensed as incurred.
 
    During 1998 and 1997, the period between established technological
feasibility and general release has been less than three months, and software
development costs qualifying for capitalization have been insignificant.
Accordingly, the Company has not capitalized any software development costs
during 1998 and 1997.
 
REVENUE RECOGNITION
 
    Information services revenues are recognized upon delivery of data and
reports ordered by the customer. Revenue arising from agreements which require
monthly reports are recognized over the period for which data are provided.
 
    Technology licensing revenues consist of technology licensing fees and
royalties. Technology licensing fees are recognized upon delivery of the
software and equipment, receipt of a signed agreement, determination that
collectibility is probable and expiration of rights of refund or return. Royalty
revenues are recognized when earned.
 
    The Company enters into certain nonmonetary transactions, in which the
Company provides services to another entity and in return receives services, or
a combination of cash and services, from the other entity. The Company
recognizes revenue and an equal amount of expense based upon the fair value of
the service provided or the service (or combination of service and cash)
received, whichever was more clearly evident.
 
ADVERTISING EXPENSES
 
    All advertising costs are expensed when incurred. Advertising expenses were
approximately $171,000 and $491,000 for the ten months ended October 31, 1998
and the year ended December 31, 1997, respectively. No advertising expense was
recorded for the six weeks ended December 31, 1996.
 
STOCK-BASED COMPENSATION
 
    The Company follows Accounting Principles Board Opinion No. 25, ACCOUNTING
FOR STOCK ISSUED TO EMPLOYEES ("APB 25") and related interpretations in
accounting for its employee stock options. In accordance with the provisions of
APB 25, compensation expense is recorded upon issuance of employee stock options
in an amount equal to the excess of the fair value of the Company's stock over
the option price. The Company has adopted the disclosure-only provisions of
Statement of Financial Accounting Standards No. 123, ACCOUNTING FOR STOCK-BASED
COMPENSATION.
 
                                      F-25
<PAGE>
                            RELEVANTKNOWLEDGE, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
2. FIXED ASSETS
 
    Fixed assets are comprised of the following as of October 31, 1998 and
December 31, 1997:
 
<TABLE>
<CAPTION>
                                                                   DECEMBER 31,  OCTOBER 31,
                                                                       1997          1998
<S>                                                                <C>           <C>
Furniture and fixtures...........................................   $   51,297   $     57,815
Computer equipment and software..................................      708,673        874,320
Leasehold improvements...........................................       87,579         84,604
                                                                   ------------  ------------
                                                                       847,549      1,016,739
Less: accumulated depreciation and amortization..................       97,788        235,855
                                                                   ------------  ------------
                                                                    $  749,761   $    780,884
                                                                   ------------  ------------
                                                                   ------------  ------------
</TABLE>
 
3. COMMITMENTS AND CONTINGENCIES
 
    The Company leases office space and equipment under noncancelable operating
lease agreements expiring through 2003. Future minimum lease payments under
operating leases as of October 31, 1998, are as follows:
 
<TABLE>
<S>                                                                 <C>
1999..............................................................  $ 309,139
2000..............................................................    245,205
2001..............................................................     97,613
2002..............................................................     66,000
2003..............................................................     16,500
                                                                    ---------
                                                                    $ 734,457
                                                                    ---------
                                                                    ---------
</TABLE>
 
    Rental expense was approximately $299,000, $136,000 and $800 for the ten
months ended October 31, 1998, the year ended December 31, 1997 and the six
weeks ended December 31, 1996, respectively.
 
    Various legal proceedings may arise in the normal course of business.
Management does not believe that there are currently any asserted or unasserted
claims that will have a material adverse effect on the financial position,
results of operations or cash flows of the Company.
 
4. CONCENTRATION OF CREDIT RISKS
 
    The Company's sales to its largest customer represented approximately 77% of
total revenues for the year ended December 31, 1997.
 
5. CAPITAL STRUCTURE
 
COMMON AND PREFERRED STOCK
 
    The Company's Restated Articles of Incorporation authorize the issuance of
up to 25,500,000 shares of $0.001 par value capital stock as of October 31,
1998. Fifteen million five hundred thousand (15,500,000) and fifteen million
(15,000,000) shares have been designated as Common Stock as of October 31, 1998
and December 31, 1997, respectively and ten million (10,000,000) and five
million five
 
                                      F-26
<PAGE>
                            RELEVANTKNOWLEDGE, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
5. CAPITAL STRUCTURE (CONTINUED)
hundred thousand (5,500,000) shares have been designated as Convertible
Preferred Stock as of October 31, 1998 and December 31, 1997, respectively. The
Convertible Preferred Stock is further designated in five series as follows (as
of October 31, 1998): 1,500,000 shares are Series A-1 Preferred Stock, 3,000,000
shares are Series B-1 Preferred Stock, 1,000,000 shares are Series B-2 Preferred
Stock, 3,500,000 shares are Series C-1 Preferred Stock and 1,000,000 shares are
Series C-2 Preferred Stock. Upon the occurrence of certain events, the holders
of Convertible Preferred Stock are entitled to convert shares of A-1, B-1, B-2,
C-1 and C-2 Preferred Stock to Common Stock on a one-for-one basis.
 
VOTING RIGHTS
 
    The holders of Preferred Stock are entitled to vote with the holders of
Common Stock as a single class and shall be entitled to one vote for each share
of Common Stock into which the Preferred Stock would be convertible on the
record date set for such vote of stockholders.
 
DIVIDENDS
 
    Upon the occurrance of certain events, holders of Series B-1, B-2, C-1 and
C-2 Preferred Stock are entitled to receive cumulative dividends. Such dividends
would be recorded based on the original issue price at a rate of 8% per annum
computed on a quarterly basis. Series B-1, B-2, C-1 and C-2 Preferred Stock have
preference over Series A-1 Preferred Stock and Common Stock in the payment of
dividends or the event of liquidation.
 
    After payment of the Series B-1, B-2, C-1 and C-2 Preferred dividends, the
holders of Series A-1 Preferred are entitled to receive noncumulative dividends
at the rate of 10% per annum of the original issuance price when and if declared
by the Board of Directors.
 
CONVERSION
 
    The Preferred Stock is convertible to Common Stock under a stated formula,
generally one share of common for one share of preferred, at the option of the
stockholder or upon the occurrence of certain events.
 
CONVERTIBLE SECURED PROMISSORY NOTES
 
    On March 15, 1998, the Company sold Convertible Secured Promissory Notes
("the Notes") in the aggregate principal amount of $3,000,000 to certain holders
of the Company's Common and Convertible Preferred Stock. The notes bore interest
at a rate of 10% per annum. Upon issuance of the Series C-1 Convertible
Preferred Stock in July 1998, the holders of the notes converted all outstanding
principal and accrued interest to Series C-1 Convertible Preferred Stock at the
same price and with the same rights and privileges as the other shares of Series
C-1 Convertible Preferred Stock. The Company issued 1,213,335 Series C-1 shares
upon conversion of the Notes.
 
    In conjunction with the sale of the Notes, the Company issued 857,122
warrants to purchase common stock to the holders of the Notes. Each warrant
entities the warrant holder to purchase one share of the Company's common stock
for $0.01. The warrants may not be exercised until the earlier of January 1,
1999 or the occurrence of certain events, including a consolidation or merger of
the Company. The warrants expire between March 2003 and May 2003.
 
                                      F-27
<PAGE>
                            RELEVANTKNOWLEDGE, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
5. CAPITAL STRUCTURE (CONTINUED)
    In connection with the issuance of these warrants, the Company recognized
interest expense of $677,126, which represents the implicit value of the
warrants (fair value less exercise price).
 
WARRANTS
 
    The Company has issued warrants to acquire shares of the Company's common
stock in conjunction with sales of Common Stock, Convertible Preferred Stock,
and Convertible Secured Promissory Notes and in exchange for services provided.
At October 31, 1998, 1,160,290 warrants were outstanding. These warrants are
exercisable at the following prices: 857,122 at $0.01 per share, 215,668 at
$2.00 per share, 38,750 at $0.06 per share, 25,000 at $0.80 per share, and
23,750 at $1.60 per share. 303,168 of the warrants were exercisable at October
31, 1998. The remaining 857,122 are not exercisable until the earlier of January
1, 1999 or the occurrence of certain events, including a consolidation or merger
of the Company. The warrants expire between April 2002 and May 2008.
 
6. STOCK OPTION PLAN
 
    The Company has issued options to its employees under the terms of The 1996
Stock Option Plan ("the Plan"). The Plan permits management to grant either
incentive stock options or nonstatutory stock options to purchase shares of the
Company's Common Stock to officers, directors, key employees, and consultants
responsible for the direction and management of the Company. The Plan authorizes
the issuance of options to purchase up to an aggregate of 1,250,000 shares of
Common Stock. Options issued under the Plan vest at rates determined by the
Board of Directors. Vesting rates can not be less than 20% per year under the
terms of the Plan. The maximum term for options issued under the Plan is ten
years. No options were issued during the six weeks ended December 31, 1996. The
following table summarizes the transactions of the Plan for the year ended
December 31, 1997 and the ten months ended October 31, 1998:
 
<TABLE>
<CAPTION>
                                                           1997                     1998
                                                  -----------------------  -----------------------
                                                               WEIGHTED                 WEIGHTED
                                                                AVERAGE                  AVERAGE
                                                               EXERCISE                 EXERCISE
                                                    SHARES       PRICE       SHARES       PRICE
<S>                                               <C>         <C>          <C>         <C>
Outstanding at beginning of year................           0   $      --      727,950   $    .442
  Granted.......................................     775,950        .446      520,038        .885
  Exercised.....................................           0          --     (245,888)       .555
  Forfeited.....................................     (48,000)       .060     (353,655)       .484
                                                  ----------               ----------
Outstanding at end of year......................     727,950        .442      648,445        .653
                                                  ----------               ----------
                                                  ----------               ----------
Options exercisable at year-end.................           0                        0
                                                  ----------               ----------
                                                  ----------               ----------
Weighted average fair value of options granted
  during the year at the share's fair value.....  $  438,444               $  109,208
Weighted average fair value of options granted
  during the year at above the share's fair
  value.........................................           0                        0
</TABLE>
 
                                      F-28
<PAGE>
                            RELEVANTKNOWLEDGE, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
6. STOCK OPTION PLAN (CONTINUED)
    The following table summarizes information regarding stock options
outstanding at October 31, 1998:
 
<TABLE>
<CAPTION>
                                                          NUMBER OF OPTIONS   WEIGHTED AVERAGE
EXERCISE                                                    OUTSTANDING AT       REMAINING
PRICE                                                      OCTOBER 31, 1998   CONTRACTUAL LIFE
<S>                                                       <C>                 <C>
$0.06...................................................         145,031          8.31 years
 0.16...................................................          50,583          8.63 years
 0.80...................................................         354,831          9.33 years
 1.25...................................................          98,000          9.84 years
</TABLE>
 
    The Company accounts for employee stock options in accordance with the
provisions of APB Opinion 25 and related interpretations.
 
    Had compensation cost for the Company's stock-based compensation plans been
determined on a fair value basis in accordance with the provisions of FASB
Statement 123, the Company's net loss for the six weeks ended December 31, 1996,
the year ended December 31, 1997, and ten months ended October 31, 1998, would
have been as follows:
 
<TABLE>
<CAPTION>
                                                        1996          1997           1998
<S>                                                  <C>          <C>            <C>
Net loss--as reported..............................  $  (143,569) $  (5,340,855) $  (6,345,905)
Net loss--proforma.................................  $  (143,569) $  (5,435,880) $  (6,418,405)
</TABLE>
 
    The amount of the pro forma charge has been determined using the minimum
value method as permitted for private companies by FASB Statement 123. For
purposes of the calculation, management used a risk free rate of return of
5.36%, a projected forfeiture rate of 0%, and an expected life of 5.1 years.
 
7. LONG-TERM DEBT
 
    In December 1997, the Company entered into a credit agreement with Phoenix
Capital under which it may borrow up to $1,000,000. During 1998, the Company
borrowed approximately $480,722 under this agreement. The note bears interest at
a rate of 20.27% and is payable in monthly principal and interest payments of
$15,191. The line of credit is collateralized by substantially all of the
Company's computer equipment.
 
    At October 31, 1998, required principal payments are as follows:
 
<TABLE>
<CAPTION>
YEAR
<S>                                                                                 <C>
1999..............................................................................  $  123,326
2002..............................................................................     148,322
2001..............................................................................     100,039
                                                                                    ----------
                                                                                    $  371,687
                                                                                    ----------
                                                                                    ----------
</TABLE>
 
8. SUBSEQUENT EVENT
 
    On November 5, 1998, the Company was acquired by Media Metrix, Inc. in
exchange for common stock of Media Metrix, Inc. The sale of the Company entitled
holders of the Series B-1, B-2, and C-1
 
                                      F-29
<PAGE>
                            RELEVANTKNOWLEDGE, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
8. SUBSEQUENT EVENT (CONTINUED)
Preferred Stock to receive cumulative dividends in the form of cash or common
stock. The majority of holders elected to receive their dividends in the form of
common stock. As a result, in November 1998, the Company paid cash of $10,509
and issued 374,424 shares of common stock to holders of Series B-1, B-2, and C-1
Preferred Stock as payment of dividends.
 
    Upon the sale of the Company, holders of options to purchase common stock
were immediately 100% vested in any options outstanding. In November, the
Company issued 480,945 shares in connection with the exercise of stock options.
 
    Also as a result of the sale of the Company, 857,122 warrants issued in
connection with the sale of the convertible secured promissory notes became
exercisable on November 5, 1998.
 
                                      F-30
<PAGE>
                               MEDIA METRIX, INC.
 
                  UNAUDITED PRO FORMA STATEMENT OF OPERATIONS
 
                          YEAR ENDED DECEMBER 31, 1998
<TABLE>
<CAPTION>
                                                               HISTORICAL
                                                      ----------------------------
<S>                                                   <C>            <C>            <C>            <C>
                                                          MEDIA        RELEVANT       PRO FORMA
                                                         METRIX        KNOWLEDGE     ADJUSTMENT      PRO FORMA
 
<CAPTION>
                                                                                      (NOTE 2)
<S>                                                   <C>            <C>            <C>            <C>
Revenues............................................  $   6,330,485  $   1,814,230  $    --        $    8,144,715
Cost of revenues....................................      4,120,569      2,879,037       --             6,999,606
                                                      -------------  -------------  -------------  --------------
Gross profit........................................      2,209,916     (1,064,807)      --             1,145,109
Operating expenses:
  Research and development..........................      1,382,375        780,277       --             2,162,652
  Sales and marketing...............................      2,888,195      1,623,500       --             4,511,695
  General and administrative........................      3,084,255      2,973,230       --             6,057,485
  Amortization of intangibles.......................        479,000       --            2,392,922       2,871,922
  Acquired in-process research and development......      1,600,000       --             --             1,600,000
                                                      -------------  -------------  -------------  --------------
Total operating expenses............................      9,433,825      5,377,007      2,392,922      17,203,754
                                                      -------------  -------------  -------------  --------------
Loss from operations................................     (7,223,909)    (6,441,814)    (2,392,922)    (16,058,645)
Interest income, net of interest expense............         65,211         95,909       --               161,120
                                                      -------------  -------------  -------------  --------------
Net loss............................................     (7,158,698)    (6,345,905)    (2,392,922)    (15,897,525)
Preferred stock dividends...........................       (313,738)      --             --              (313,738)
                                                      -------------  -------------  -------------  --------------
Net loss applicable to common stockholders..........  $  (7,472,436) $  (6,345,905) $  (2,392,922) $  (16,211,263)
                                                      -------------  -------------  -------------  --------------
                                                      -------------  -------------  -------------  --------------
Basic and diluted net loss per share applicable
  to common stockholders (Note 3)...................  $       (0.98)                               $        (1.49)
                                                      -------------                                --------------
                                                      -------------                                --------------
Shares used in calculations of basic and diluted
  net loss per share applicable to common
  stockholders (Note 3).............................      7,618,511                                    10,860,906
                                                      -------------                                --------------
                                                      -------------                                --------------
</TABLE>
 
     See accompanying notes to unaudited pro forma statement of operations.
 
                                      F-31
<PAGE>
                               MEDIA METRIX, INC.
 
              NOTES TO UNAUDITED PRO FORMA STATEMENT OF OPERATIONS
 
                          YEAR ENDED DECEMBER 31, 1998
 
1.  BASIS OF PRESENTATION
 
    The unaudited pro forma statement of operations gives effect to Media
Metrix, Inc.'s ("Media Metrix") acquisition of RelevantKnowledge, Inc. ("RKI")
as if it occurred on January 1, 1998. Such unaudited pro forma financial
statement sets forth the historical results of operations of Media Metrix for
the year ended December 31, 1998 and of RKI for the ten months ended October 31,
1998. The operations of RKI for the two months ended December 31, 1998 are
included in the operations of Media Metrix.
 
    The unaudited pro forma statement of operations has been prepared by
management and should be read in conjunction with the historical financial
statements of Media Metrix and RKI. This statement does not purport to be
indicative of the results of operations that might have occurred if the RKI
acquisition was consummated on January 1, 1998, and does not purport to be
indicative of future results.
 
    Management believes additional synergies and operational improvements, not
reflected in the accompanying unaudited pro forma statement of operations, will
be realized by the combined companies. Such amounts cannot be reasonably
quantified and, therefore, are not reflected in the unaudited pro forma
statement of operations.
 
2.  PRO FORMA ADJUSTMENT
 
    The pro forma adjustment reflects the additional amortization required for a
full year's amortization of the intangibles acquired. Total intangibles were
approximately $6,216,000 of which $1,200,000 was allocated to panel costs with a
life of 12 months and the balance was allocated to goodwill and various other
intangibles with lives of 3 years. The annual amortization consists of the
following:
 
<TABLE>
<S>                                                               <C>
Panel costs.....................................................  $1,200,000
Goodwill and other intangibles..................................  1,672,000
                                                                  ---------
Total amortization..............................................  $2,872,000
                                                                  ---------
                                                                  ---------
</TABLE>
 
3.  NET LOSS PER SHARE APPLICABLE TO COMMON STOCKHOLDERS
 
    Pro forma net loss per share applicable to common stockholders adjusts the
weighted average shares outstanding for Media Metrix's historical financial
statements for the shares issued to RKI stockholders as if such shares were
outstanding for the entire year.
 
                                      F-32
<PAGE>
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
MAY 7, 1999
 
                                     [LOGO]
 
                        3,000,000 SHARES OF COMMON STOCK
 
                              -------------------
 
                              P R O S P E C T U S
                              -------------------
 
                          DONALDSON, LUFKIN & JENRETTE
                         BANCBOSTON ROBERTSON STEPHENS
 
                           THOMAS WEISEL PARTNERS LLC
 
                                 --------------
 
                                 DLJDIRECT INC.
 
                               E*TRADE SECURITIES
- ------------------------------------------------------------
 
We have not authorized any dealer, salesperson or other person to give you
written information other than this prospectus or to make representations as to
matters not stated in the prospectus. You must not rely on unauthorized
information. This prospectus is not an offer to sell these securities or our
solicitation of your offer to buy the securities in any jurisdiction where that
would not be permitted or legal. Neither the delivery of this prospectus nor any
sales made hereunder after the date of this prospectus shall create an
implication that the information contained herein or the affairs of Media Metrix
have not changed since the date hereof.
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
Until June 1, 1999 (25 days after the date of this prospectus), all dealers that
effect transactions in these shares of common stock may be required to deliver a
prospectus. This is in addition to the dealer's obligation to deliver a
prospectus when acting as an underwriter and with respect to their unsold
allotments or subscriptions.
- --------------------------------------------------------------------------------


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