Elastic 2 column XHTML and CSS layout

This is a slight modification of Roger Johansson's code that I found while reading [this article](http://www.456bereastreet.com/lab/developing_with_web_standards/csslayout/2-col/). I've modified the code to use ems instead of pixels. [Mike Jolley](http://blue-anvil.com/archives/going-elastic-with-ems-layout-techniques) has written about why ems are preferrable over pixels. ```html
Content
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