You have 11 images without alt tags.
see
http://validator.w3.org/check?verbos...t-print.org%2F
I think you will find that most of these are your menu gifs.
Even spacer gifs need an alt tag. alt="" will validate. However, it is better to have an alt tag as not only will the site be fully accessible to those with a visual impairment but will be visible to search engines.
However, if you have a look at the above link you will find a whole bunch of other html markup errors (34 in total) for you to have fun sorting.
If you need any further assistance here correspond thro a pm.
Cheers
Ian