Vertical Sizing Past 100%

I have a two column layout in the center of a page, which is vertically sized to 100%. Everything looks fine until content is added which exceeds the height of the page. The column containing the overflow will be extended, but borders and backgrounds of other columns will remain behind. In Mozilla, the backgrounds and borders of the overflow column don't even extend, just the content.

How do I make everything extend with this column?

Here is the site in question. The green column's content exceed the size of the page. I would like every column to match the green.

Thanks