100% div height with CSS

Getting 100% height on a page with CSS can be a bit tricky, either you don’t get it or you really get it (meaning the page is has 100% no matter how much content you have and cuts off any excessive content).
Many still think (I’m writing this 2012) that this is a good argument for using tables in their design. These are the same people who think that IE6 still has value and that flash is the future. It’s not so hard, though, to do with CSS and I’ve come up with a demo where I get 100% height by just applying the correct CSS (the text is still in Swedish as I wrote it some time ago but it basically says somethings about css that’s not so important, the CSS is there and the source is just a right-click away):