GIF89a
A standard introduced in 1989 that was introduced to replace the original GIF87a. The GIF is commonly referred to as an animated gif because of it's ability to create animated pictures as a single image. However, in addition to this ability this new standard also gave the capability of transparent images.
In the animated image to the right, the animated gif prints out "Computerhope.com Free computer help!" if the browser supports it and animated images are enabled.
Also see: GIF, Transparent