Comment 5 for bug 1273208

I don't see how it might help. I tried to set height: 100% on #main_content, body and html (which is exactly the same as i understand it), but then you will hit the bottom edge of the window and you would need to manually create a gap for action menu by padding or margin, and then someone else change number of elements in menu and you'll need to change it again...

The real problem here is that overflow:hidden creates new context and cuts off anything that hang outside of it (same as iframe). Another css property that creates new context is display:table, but as opposed to overflow:hidden it doesn't cut off any contents that hangs outside of it. All you have to do is to make sure your block will took all the space left. To do that, we create additional block (:after) that consist of two characters (dots) with the space between them equal to 99in (about 10k pixels, way bigger than any display around). Then we make sure no one except for the browser will see this block and fix some nasty bug in Opera 11 and 12.

This solution are much wider supported by browsers than vh and it fixes all the cases this issue appears.