Pop-up, pop-under, and in-line ads have been said to be intrusive, and previous findings suggest that they could have important effects on user perception and cognition. Using a 2x2 factorial design, this experimental study examines the effects of those ads. Besides a control group without ads, factors included ad placement (pop-up vs inline) and ad congruence (with the site's content or not). Results indicated that intention to return was impaired by ads; retention of website information was higher when ads were inline or when ads were not congruent with website content; and retention of ad content was higher for inline ads and those that were not congruent to the content of the website. However, contrary to expectations, intentions to return were not affected by ad placement, retention of site content was not affected by the existence of ads, and intrusiveness of ads was not affected by ad congruence.