Using ALT Text To Identify Graphic Images

What is alt text?  It's a short text description of a graphical element (picture, image, photo, graphical link, etc) on a Web page. The use of alt text on an image is a Section 508 requirment, unless the image is purely decorative. See the Accessibility web site for information how to properly implement the alt text attribute.

Optimizing Graphical Images To Improve Download Times

You should try to keep the file size of graphical images small enough to load "reasonably quickly". Think about the user on the other end who's using a slower dial-up connection. Weigh the trade-off between the information or stimulation created by graphics vs. slow download. Read about which file types to choose, which file types require less storage space, and which file types load faster, read the guidelines for still images.

More information on this subject is available in the article titled Graphics at the Website.