CSS: 100% layout height with fixed header

[VictorFreriks]

I have a design that has a centered div that stretches across the entire height
of the browser. Within this div I have a header div with navigation inside it
and a div containing the main content. But when I add the content, sometimes it
exeeds the page height and I'd like the text to overflow in that case.

In short; how do I set up the div containing the text to be 100% high minus
the height of the header div?

Thanks in advance,
Victor