How can we give a DIV height 100% in a tableless layout ?

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I have a site made using DIV tags. The problem is right now I have given a specific height to a div. But what if the content is more then how to give div tag 100% so that the div takes the rest of the area by itself. I tried giving 100% through css but not working. Below is the example. I am talking about the right links. That div is right now given a specific height. What If to make that DIV height 100%