How can an html element fill out 100% of the remaining screen height, using css only?

Question

I have a header element and a content element:

#header
#content

I want the header to be of fixed height and the content to fill up all the

Answer 1

With HTML5 you can do this:

CSS:

body, html{ width:100%; height:100%; padding: 0; margin: 0;}
header{ width:100%; height: 70px; }
section{ width: 100%; height: calc(100% - 70px);}

HTML:

blabablalba 
 Content