CSS float causes containing div to not extend full height

We have a page with the following setup:

<div id="wrapper">
<div id="col1">
content
</div>
<div id="col2">
content
</div>
<div>

We use float: left on col1 & col2 for positioning.  There is a background color applied to "wrapper", however we are finding that the height of "wrapper" does not extend the full height of the content in col1 & col2.  We've spent all day trying variations and breaking the markup & styles down, having trouble determining why the container div does not extend.

Here is an example page: http://hovercrafts.d3t.biz/content.html

You can see the main content area has a content and a sidebar.  The light-colored box near the content is supposed to be the full height of the content area (it is a container div for the content area).

Any thoughts on what we are doing wrong?  I'm sure it's something obvious, but we are missing it.  Thanks.