The initiation of keyword advertising has had a remarkable effect on online advertising, Internet marketing, search engines, and Web sites that earn advertising revenue. In a discerning article, Rust and Varki (1996) argued that “interactive media, particularly the Internet, would change the traditional paradigm of mass media advertising to heterogeneous audiences”. Among their forecasts, they claimed interactive media would allow individual consumers to access pertinent information easily, non-sequentially, and on demand. Interactive advertising would be targeted, by invitation, and accountable. Keyword advertising exemplifies this very prediction because the advertisements a user sees are targeted on the basis of specific keywords. The user accepts the invitation to see the advertiser's Web site by clicking on the ad, and every click is accountable.
New media tends to emulate earlier media, and just as early television broadcasts resembled radio broadcasts (Bezjian-Avery et al, 1998), early Web site advertising resembled traditional mass media advertising. Online advertising charged according to impressions, that is, how many people could possibly see an advertising banner on a Web page. This model stemmed from the mass media concept of cost per thousand (CPM), and rates ranged from $10 to $100 per thousand impressions (McCarthy, 2008). Yet CPM ignores whether the Web site visitor saw, or clicked, the ad banner.