Also referred to as a banner ad, a banner is a typically rectangular advertisement placed on a Web site either above, below or on the sides of the Web site’s main content and is linked to the advertiser’s own Web site. In the early days of the Internet, banners were ads with text and graphic images. Today, with technologies such as Flash, banners have gotten much more complex and can be ads with text, animated graphics and sound. Most commerce-related Web sites use banner ads.
See interstitial, hyperstitial and SUPERSTITIAL.
Also see “How Affiliate Marketing Works” in the “Did You Know…” section of Webopedia.