The HTML 5 Image Element
http://juicystudio.com/article/html5-image-element-no-alt.php

Lemon, Gez
Juicy Studio
2007

Abstract:

One of the great things about the current HTML 5 draft is that they give plenty of examples of how to specify alternate text for images, although a few of them are misguided. Alternate text should be concise, and a longer description provided with a longdesc attribute if necessary.