====== clearing floats ======
By default, a containing element with floated children will not extend to the bottom of the floats because the floats are removed from the flow of the page.  To fix this, I typically put an element at the bottom of the containing element, after all floats, with the style "clear: both;".

There are some other ways to achieve this, and the above method may not work in all browsers.  See the links below.

===== External Links =====
  * http://www.positioniseverything.net/easyclearing.html
  * http://www.sitepoint.com/blogs/2005/02/26/simple-clearing-of-floats/
  * http://drupal.org/node/380906