A Fortune Magazine article from August 2007 explains the difficulties advertisers face in measuring online advertising. Internet advertisers have long billed the internet as one of the most accountable advertising mediums, however, discrepancies in reporting among major ratings and research firms suggest advertisers should be discerning in using web measurement company metrics to support advertising decisions.

Given the constant change in internet user behavior, combined with the addition of new technology available to users, discrepancies in internet data is inevitable. With the lack of standards in measurement, Randall Rothenberg, CEO of the Interactive Advertising Bureau, recently called for an audit and accreditation process for web measurement companies. Until the time of standardizing comes, it is important for online advertisers to use multiple sources when making media buying choices and to understand that it is still less than an exact-science.

Read the full article, The Online Numbers Game, at CNNMoney.com