There are several alternate solutions for this, by the way. One of them is to use @media queries to target browser width < 1302px, which cause the left two columns to collapse to the top (you can see a vague emulation of this by removing overflow-y:hidden from section#container, which will simply show you that, in Firefox, the content box will collapse underneath the left two divs). That is the source of the problem you're all experiencing, in any case.