The longdesc attribute of an <IMG> tag is a link to another document that describes the image. This is suitable for complex and technical images. For example, the image of an integrated circuit (IC) may convey information including the meaning of each pin of the IC. A short description (alt attribute is not sufficient). A separate HTML document can be used to describe the assignments of the pins.
Listing 2 is an example of such an image. This listing is in the context of the <BODY> portion of an HTML document.
| Listing 2: | longdesc |
Note how the filenames of the image and the long description HTML document match each other. This is not only helpful for a screen reader program, but also for the author of the web page.