Stretching Content Width

Hi, Was running this theme on a previous build of my site and was wondering how to stretch content to how I had it prior on my pages. What I mean is, when there isn't a sidebar, stretching the page content to were the sidebar would be. It worked before, perhaps on an older version, but now I cant figure it out. Take a look at my site. The dark area on the bground image is how wide i want the content to be. http://www.axongaming.org Thank you!