Centered site. (Like cnn.com)

So while i was putting together my site i ran into a problem with centering. As you can see on cnn.com, as you make the site smaller the "content" stays centered until you make the page small enough to touch the left edge. When the "content" on the site hits the left edge it freezes. The page then proceeds to shrink without adjusting as you make it smaller. Any thoughts? I would like to learn how to add this feature to my site.

Thanks

-alex