The skin of your forum, look a bit boring, maybe a change will make it lively,
I normally prefer google ads not at the side but at the top or at the bottom of the page.
The forum looks empty, and the categories and forums do not make sense.
And there are just 2 categories to discuss like yui and webdesign.

Try recreating your forum categories by checking out some developer sites, maybe then you will get the idea of making one.

My first impression of your site is that it took a while to load. Im not sure if that is my connection or your site though. The template and color on the forum seem very boring and common, making me not want to stay.