It looks nice - fairly clean & simple (no blink tags, etc ;-))
In IE7, the left-nav doesn't appear at all - making it impossible to navigate.
The left-hand navigation 'hover' state colour might not be visible enough to some people - I think the contrast between the light green and the background colour isn't enough - so it might be worth darkening this up a bit. The same goes for other link hover colours, too (e.g. contact link, etc).
There is also no visual feedback on the nav about which section you are currently in (although there is a title on the page, most people would look to the nav for this, IMHO).
Are the "font-" and "font+" links of much use? Most users are probably aware of how to change the font size, and the links on the page only seem to go 4 steps.
For some reason, in Fx on any page with the image 'popups', when viewing the large images, if you click on the image to close the view, the image "jumps" about 10 pixels up before returning... this doesn't happen in IE 7, though.
I do like the picture in the top-right of the screen - it's quite a nice touch.
Hope this helps,
Dan
Coedit Limited - Delivering standards compliant, accessible web solutions
[tt]Dan's Page [blue]@[/blue] Code Couch
[/tt]