CofC Web Accessibility Guidelines- Rule (E)

(e) Redundant text links shall be provided for each active region of a server-side image map.

Translation: If you use server-side image maps, you should provide text links that provide the same access.

Some background: An image map is a picture that's been carved up into pieces. An example would be a map of the US where clicking on each state took you to a different page. It looks like one big picture but in reality each region is linked to something different.

When using a client-side map, the image and all it's associated markup is actually stored on your computer when you load the page. Not only do we get the picture, but we also get the information that tells us how the picture has been sliced up.

A server-side map is different. Only the picture is loaded. All the information about how the map is chopped up resides on the server. When the user clicks on the graphic, a set of co-ordinates are transmitted to a program on the server and some action is taken. Since only the picture is loaded, any clues as to what the various parts of the picture do will not be available to an alternative browser.

What to do: Use client-side maps whenever possible. This is pretty easy since server-side maps are seldom used anymore. If you must use server-side maps, be sure to provide text links that provide the same function.