Stretch the post content closer to sidebar

My forum is located at : http://www.337studios.com and if you can notice, all the post content is kinda squished to the left side and there is alot of room between it and the sidebar, Im looking at it through IE cause firefox doesn’t work at work so I was wondering how can I fix it to utilize more space to reach the content closer toward the sidebar without messing it up any? Help if you know, thanks!