To start with, good work on the css file. I looked it over in FireBug and it looks like it took quite some time to do (860 somethin lines in the primary css file!). I don't like that it's done in tables (Made me cry a little in the inside to see in a web developer), but the sin is forgivable given the level of skill this site is designed at. There is a slight bit of messy code that I found on w3.org.
http://validator.w3.org/check?uri=h...(detect+automatically)&doctype=Inline&group=0
That should give you line numbers and the whole nine yards you need to clean up your code a bit.
All in all I give the site a 3.8/5. It would be a 4.8, but I always subtract a whole point for large amounts of code. It's not a huge issue here, but I was still very aware of it. You kept your number of HTTP requests to a minimal though, which I applaud. Your page size (not counting size of each image loaded) comes out to around 11KBs. Once you start calculating in CSS and images it can slow down a bit (took nearly 3 seconds for me to load, but I'm running wireless).
The flow and general "pop" of the site is well managed. You arranged things with a plan in mind and kept the important things where they need to be, mostly.
Color management is good, and nothing is too hard on my eyes (given my eye sensitivity, that's a feat). Everything contrasts well, so I can read it. There's not too many dark colors, but rather lighter colors that make people tend to stay on the site longer. Lighter colors add for a lighter feel which create a lighter, more carefree mood. Dark colors (although not bad) are naturally opposite. Good job using lighter colors here
