I'm not an "expert" (just ask several others here) but I can tell you one thing. The bottom half of the page, with the light grey background and slightly darker grey text is a nightmare on an LCD screen to read. Imagine a tablet out in the sunlight.
Check out design mistakes from webpagesthatsuck.com
There are some doozies for contrast mistakes there.
Agreed, it's very difficult to read the bottom half. In addtion, the entire site was built with ap divs which is a big mistake. Looks what happens when a visitor has the text sized differently than you designed for. There is no need to use AP divs for anything on that site.
I'll follow in line with everyone else about the bottom half.
Now to add to Bregent's comment, by making absolute positioned divs with defined heights and widths, you actually have text falling outside of those boxes in Safari and Chrome which looks bad.
Then you have the top menu in bright green and blue, but the submenu and everything else on the page is a plain gray and your logo is red. There appears to be no continuity in the design at all. This will be very hard to build a brand around. Then with the menus you can't even tell where there is a 3rd level because the arrow image blends in so much.
The last thing I noticed is a validation error that sticks out:
What is a <wbr> tag for? You have it twice on 177 and 199 (after PHP processing). Browsers may interpret that strangely because even in HTML5 custom tags are not really allowed as far as I know.