The effects of online advertising

Scott McCoy, Andrea Everard, Peter Polak, Dennis F. Galletta: The effects of online advertising, Comm ACM 03-2007

"Our findings suggest that advertisements do have significant effects on retention of the site. Also, advertising content that is non-congruent with the site’s content seems to lead to greater effort in reconciling the differing content, and ultimately greater memory of both the Web site and the advertisement. Intrusiveness is also important for both Web site designers and advertisers. Pop-ups and pop-unders seem to be more intrusive than in-line ads, implying
that users should not be interrupted from their online tasks to close the extraneous windows.
[...]

Designers should realize the magnitude of ill effects caused by advertising.
Although some of the differences were not large in magnitude, reducing the likelihood of a person’s return by 11% might be a cost that is too great for a site host to bear. Discovering that pop-up and in-line ads differ greatly in measures of intrusiveness, a host might play it safe and make use of in-line ads. As theory and practice begin to converge in this area, perhaps
what has been described so often as a wild new frontier might finally take a few steps toward being tamed."