GIFs - Animated GIFs, Transparent GIFs, Interlaced GIFs
Dithering GIF Images
Dithering in GIF images helps reduce banding in gradients of color, but it also vastly increases the file size. This gallery demonstrates how large the images can get with dithering and no dithering.
The day the GIF patent expired.
Make Smaller GIFs
The smaller you can make your Web images, the faster they will download. This how to from the Graphics Software Guide will help you make your GIF files as small as possible.
Optimizing GIF Images
Comparing the file sizes for vertical lines in a GIF file to horizontal lines in a GIF file.
Types of Web Files - Graphics and Images
An explanation of the primary graphic file types for the Web.
Antialiasing, Transparency, and the World Wide Web
This tutorial covers both anti-aliasing and transparency. These are important in combination, because if anti-aliased poorly, transparent images will appear to have a halo.
Transparency - What is it?
This tutorial explains what transparency is, and gives some simple tools to create transparent images.
Web Style Guide: GIF files
This is a great overview of what a GIF file is and how they work. It covers interlacing, transparency and animation.