A web banner or banner ad is a
form of advertising on the World Wide Web. This form of
online advertising entails embedding an advertisement into a
web page. It is intended to attract traffic to a website by
linking them to the web site of the advertiser. The
advertisement is constructed from an image (GIF, JPEG, PNG),
JavaScript program or multimedia object employing
technologies such as Java, Shockwave or Flash, often
employing animation or sound to maximize presence. Images
are usually in a high-aspect ratio shape (i.e. either wide
and short, or tall and narrow) hence the reference to
banners. These images are usually placed on web pages that
have interesting content, such as a newspaper article or an
opinion piece. -- wikipedia.com
Here's
a list with more information about Banner Ads. Check it out.
