“The Effects Of Online Advertising: Consumers’ First Impressions (and Loyalties) Are Made in the Opening Moments of a Web Site Visit and the Degree to Which That Visit May Be Intruded by Pop-Ups, Pop-Unders, and Banner Ads”, 2007 (; backlinks):
We conducted an experiment with different forms and types of ads. An artificial Web site was created for the experiment that contained images, prices, and descriptions of familiar products and product categories. The products were those that would be carried by a general store and included food, health care, and household products. Nine search tasks were assigned to participants that would force them to traverse a variety of portions of the site…The experimental websites were accessed over the Internet in a controlled laboratory setting by 536 undergraduate students.
…This study provides clear support for an assertion that users will adopt more negative intentions when a site displays advertisements than when the site does not. It is also clear that advertisements interfere with retention of site content and that features of advertisements also have important effects on retaining both site and ad content. Inline ads permit both site and ad content to be remembered more clearly than popups and popunders, a finding that is most interesting because it suggests the action of closing the advertisement window distracts users from the site, and further, it is visible for a shorter time. When ads are markedly different from the content of the site, they theoretically stimulate more effort as users work toward an important goal, and users remember more about both the Web site and the advertisement.
It is interesting to note that while these effects might on the surface appear small, they are quite consistent and highly statistically-significant. Extrapolating to millions of site visitors, even small differences can amount to an urgent problem for management. Finally, it is also clear that popups and popunders are considered to be more intrusive than inline ads. Users seem to prefer not to have to divert their attention from their searching task or take additional steps to close the popup or pop-under windows.