Note that the constant flapping is a distraction.

Originally developed as a layered Compuserve format, gif's can display images on separate layers one at a time, in series.

Since the human eye tends to let images persist, if the display timing is 12 frames per second or greater, the resulting series of images has the illusion of motion.

These animations do not require browser plug-ins, so they deliver motion to most browsers without the difficulties associated with Flash. However, unless the composit image has a very large number of frames, the resulting image lacks the fluidity of Flash.

Because the layered image begins to display as the download progresses, an image with many frames may end up stuttering over slow connections.

To limit the "weight" most animated Gifs are necessarily small using a limited color pallet, so Gif are best suited for images that do not require subtle shadings of color.

Animated gifs should be used sparingly, and then only if they convey content in addition to motion.