Andrew Moreton's Web Publishing Resource

D-links

Use D-links to provide detailed descriptions of images where the alt tag will just not do.

A D link is a [D] with a link pointing to a description of a graphic's content.

The alt attribute of the img tag is used, as all righteous folks know, to describe visual material for non-visual browsers.

As there could be some bad eggs/uninformed characters out there haven't been adding this required attribute to their images I'd best quickly explain.

The WWW is supposed to be open for use by as many people as possible and quite a few people have problems with images in web pages — maybe because they're visually disabled, maybe because they don't have a modern graphics-friendly computer — whatever — for a variety of good reasons sometimes people can't see the pictures on your pages.

To counter this the tag which displays images in HTML — the img tag has to have an attribute providing a text alternative to the image — so called 'alt text' — that can be rendered by a non-visual browser. It looks something like this:

<img alt="A description of the image" />

The problem with this is that it doesn't leave much room to describe much, especially when many visual browsers will display an alt value as a pop-up tool-tip style device that floats above an image.

Thus was the longdesc attribute invented. longdesc is another img tag attribute pointing to a separate URL containing a full description of the image on your page. The trouble with longdesc is that very few browsers support it. If you were to use it looks something like this, but don't expect it to work many places...

<img longdesc="full_description.html" />

Because longdesc doesn't work various access ability advocacy groups are evangelising the use of the D-link — a bracketed D — [D] that sits next to an image and provides a link to a page describing the content of the image.

Here's what it can look like: the [D] is just a normal link to another page with the code looking a bit like this: