Web Design in a Nutshell, 3rd Edition

Server-Side Image Maps

In the first years of the Web, all image maps were server-side image maps (client-side image maps were introduced later). Because they rely on the server, they are less portable and the information is not self-contained, which introduces serious accessibility problems if the server is not available. As of this writing, the use of server-side image maps is strongly discouraged.

For historical interest, a description of how they work is provided here. Server-side image maps have four elements:

• An ordinary image file (.gif, .jpeg, or .png).

• HTML markup in the document: the ismap attribute within the img element and an anchor (a) element that links the image to the .map file on the server.

• A map definition file (.map) containing the pixel coordinate and URL information for each clickable area; the .map file resides on the server, usually in a directory called cgi-bin. The map file format is server-dependent and may be formatted as either “NCSA” or “CERN.”

• A CGI script that runs on the server (or a built-in function of the server software) that interprets the .map file and sends the correct URL to the HTTP server.

Within the HTML file, the image map is set up as shown in this example:

<a href="/cgi-bin/imagemap/spacey.map"><img src="x.gif"ismap /></a>