Major_Payne - 2:59 am on Sep 8, 2010 (gmt 0)
That's an important point, but I have noticed too many pages that have an alt="" attribute that is blank just so it passes the validator.
the SE's will happily read the alt attribute value and use it for header tag content.
With no text, SEs will miss it. Others put in badly worded text which IE wrongly displays as a tooltip on a mouseover and SEs will not make much sense of. It might be better to include the title="" attribute along with the alt="" so other browsers can correctly supply the mouseover tooltip and the SEs may take more notice of the "heading" text within the title attribute than the alt.
Of course, the title="" can be put in the image or the heading tag.
Sorry if I appear hard-headed about all this. Guess I am a code-nazi. :P