Basically, 100% height will force the block element to expand to fill the available vertical space available to it regardless of the content.
It’s useful for making ‘full screen’ web pages, you know the ones where the footer isn’t halfway up the screen. There are other uses but did you have a more specific question?
I really don’t use it unless I have to…and I don’t have to often.
So … does that mean you could use height:100% to resolve issues with the 2 column layout? Just set both columns to height:100% and they’ll stretch to fill the parent wrapper, yeah?
It makes sense in my head, but it can’t possibly be that simple … can it?