i mean making it stretch vertically to (at least) 100% of the screen. check out one of the pages that doesn't have a lot of content, like http://www.learningquickly.com/new-site/contact.html. if your res is set to a higher value like 1280 by 1024, it doesn't stretch the whole height of the screen.
Do you mean that you want the content box to stretch all the way to the bottom of the screen even if that area does not have much content in it? If so, add height:100% to your content div.
It should look like this: