I agree with CAMS that the slogan under the logo is hard to read. I have absolutely no idea what it says
The forumhome is very ads heavy IMO, which is a big turn off.
You have a lot of empty forums, so I would have started out with less and added to them as the site grows.
I like the style of your style, but personally I find the color combination a bit strange.
A couple of things that puzzle me:
-> Why have you got the guest welcome message in the navbar and on the forumhome? It is duplicated content.
-> Your navbar buttons are unequal width. Is there a reason for this?
Finally, in your footer, you haven't wrapped the usercp link with the show member condition, so it is showing to guests.