Editing Width of Theme

I am attemping to edit the theme and I’ve run into a bit of a snag. The width of the content (sidebar and post/page) are not truly fluid – they’re set at a set width and if I drag the page smaller or larger, the content stays at a certain width, then drops to the next lowest or highest. Can I remove this so the content narrows properly like it does in the mobile version?

My site: http://gsmadvice.com