A Brief Look at some competing media formats on the web.

Name	Color Depth	Transparency		Stuff
GIF	<256 colors or less	single level transparency built in animation well established in browsers/editors	proprietary limited to 256 colors	Ideal for icons, the gif is not area compressed so text still has crisp edges, the 256 color limit hinders photos, but is useful for limiting page bandwidth/download time. Built in animation capabilities but is not any more useful than any other graphic for creating more advances user interfaces (say like changing graphic on mouse click)
JPG	<24 million colors	no transparency well established in browsers/editors	no transparency animation only by java or other code	Ideal for pictures, large scale image mapes. Area compressed meaning that flat areas of color may become blotched, and edges of text blurred. (meaning you will have to use larger fonts in order to be readable. Is a propritary format, although that doesn't seem to be stopping anybody from using it.
PNG	<24 million colors	multi-level transparency (alpha channel)	not well established in browsers	Potential to take the place of both jpg and gif for 2D graphics
VRML	24 million colors	multi-level transparency (effectiveness depends on users hardware/software (since it's a rendered technology)	requires a plugin for 3.0 browsers	A 3D format, capable of interactive animation, 3D sound placement, with extremely small structural file sizes (media like texture maps using jpeg, or audio/midi files still take up the same amount of space).