The meaning of alt text is to serve as replacement (hence, “alternative”) when the image the HTML intends to serve cannot be seen. There’s a variety of reasons for that to happen; the user is blind, the medium doesn’t support images, the user disabled images on purpose so she can browse on low-bandwidth, or the Googlebot comes around to visit.

For example, when your image is a mere illustration to a point you’re repeating elsewhere in the text, there’s no need at all to use the alt text. Because the image is not crucial to understanding the point. Most people however at this point heard some rumors that the “alt tag” is increasing accessibility; and possibly, they’ve heard somewhere else that accessibility is professional these days. And they also might want to see a tool-tip, not knowing that the title attribute would come in handy for that. (Wordpress in typical installations even creates an alt text based on the image’s file name; tools like Frontpage have committed similar silliness in the past.)

So, let’s say our blog post is titled “New AJAX Flavor Discovered” and the illustration following the headline is a shrink-wrap box with the shiny colorful letters “AJAX,” then repeating the letters AJAX in the alt text will result in something like this within alternative browsing contexts:

New AJAX Flavor Discovered
AJAX

Is this useful? No – the point of the illustration was to use a recognizable catchy visual, or to suggest that AJAX is hyped as a shrink-wrapped shiny product; the point was not to clarify (in text) that the article is about AJAX, as the headline already did a good job at that.

In XHTML2, by the way, some of us may be able to get rid of the alt attribute altogether. Why? In XHTML2 you can use the “src” attribute on anything, including e.g. a paragraph. It’s a bit like longdesc (today’s link to a longer image description) done right.

Misunderstand Web Standards