I wonder how you get to that number of errors but I'm sure you are not using W3C to find them.
I find 336 errors and 81 warnings in your portal page, 215 errors and 32 warnings in your index page and 75 errors/72 warnings in your css
EDIT: and this is only when W3C views what a guest can see!!! I expect even more when it sees what member can see, mod can see, admin can see.
PS... and ofcourse this is only on those two pages, you can check any page for more