Without seeing your CSS it is impossible to tell, but make sure you aren't defining widths for your DIVs unless they are defined properly, and check for elements within the DIV which could be causing them to expand.
The reason for that be the div size greater than the page and it results in scroll bar.If you do overflow:hidden ,it will not fix error,but just hide it.
So better fix the size of your container.
I can't see the problem in your site so can't tell the exact fix for it.
I agree with AHarrisGsy. I don't see any problem with your main-wrap div being 968px. It is within the range of most resolutions people are using today. If you set it to 100% be prepared to start adjusting all the other divs inside of it that were designed with the idea that main-wrap would be a fixed width.