如何强制一个DIV块扩展到页面的底部，即使它没有内容?

In the markup shown below, I'm trying to get the content div to stretch all the way to the bottom of the page but it's only stretching if there's content to display. The reason I want to do this is so the vertical border still appears down the page even if there isn't any content to display.In the markup shown below, I'm trying to get th