Hello, how do i make the height of the child div the same as the parent height, bearing in mind that it will be dynamic. The page i want to do this on is shown below. It is the footer with the smaller grey boxes.

http://www.benwebdeveloper.com/test/?cat=1

height: 100%;

doesn't do anything at all....

Why not use fixed height?

could do i suppose.

a greater technique than fixed height (wich is not very useful is you say that content is dynamic) is "faux columns" tehnique. You'll find more infos and tutorials over the internet. The basic ideea is that you'll repeat-x a full width background in parent div. This way you'll get equal size columns.

The 100% should work - unless you have padding on the parent div, which it looks like that footer might have.