GIF 
Graphics Interchange Format 
Most color images and backgrounds on the Web are GIF files. Most often pronounced "djif"(soft g) but also called "giff" (hard g), this compact file format is ideal for graphics that use only a few colors (the GIF format is limited to 256 colors), and it was once the most popular format for online color photos--until JPEG came along. JPEGs can contain up to 16 million colors, and they can look almost as good as a photograph.

CompuServe developed GIF in 1987, calling it GIF87, and two years later, it added new features such as interlacing, transparency, and animation to create the format known as GIF89a. People don't usually distinguish between the two GIF versions, so if someone refers to an image as a GIF89 rather than simply as a GIF, it's probably animated. Unisys developed the LZW compression scheme used for GIF files and has collected licensing fees for the technology since 1994; however, its U.S. patent expired on June 20, 2003, and its international patents will all expire by mid-2004.