Unfortunately, Macintosh and Windows reserve different colors for all palettes. The overlapping number of colors is referred to as browser-safe colors and they total 216. Most graphics applications provide an option to create images using the browser-safe or web palette. The GIF specification includes some special features that allow the creation of different types of GIF files. Transparent GIFs Transparent GIFs blend in smoothly with the web page background permitting irregularly shaped images.
Transparency is obtained by assigning one color to be transparent.
Interlaced GIFs Interlaced GIFs provide a lower resolution image first and then improve the resolution until the entire image has arrived. This is as opposed to arriving linearly from the top to bottom. Web designers use this feature to provide quick preview of what the entire image will look like. Animated GIFs Animated GIFs are a series of GIF's displayed one after another on top of each other. Animated GIFs are simple to create and are sometimes a good alternative to other types of animation because no other programs or plug-ins are needed for the animation to work.