How to force child div to be 100% of parent div's height without specifying parent's height?

Question

I have a site with the following structure:

  

  <         


        
      

Answer 1

[Referring to Dmity's Less code in another answer] I'm guessing that this is some kind of "pseudo-code"?

From what I understand try using the faux-columns technique that should do the trick.

http://www.alistapart.com/articles/fauxcolumns/

Hope this helps :)