Banner
An advertisement in the form of a graphic image that runs across a Web page or along a margin.
Banner ads are usually GIF images, static or animated. The most common standard banners: large - 468 pixels wide by 60 pixels high, medium - 125 by 125, and small - 120 by 90 pixels.
Vertical ads (skyscraper ads) are usually 120 x 240, 120 x 600, and 160 x 600. Pop-up and pop-under ads are most commonly 250 x 250. Leaderboards are the widest, running 728 x 90. Rich media ads are animated banners which use Flash animation.