CSS

CSS styling DIV height when using float

Old solution

The old solution to this problem required you to add an extra element with clear: both to the container. Once it was in place the container contained a non-floating element, which means it stretches itself up to accomodate it.

The new solution

The width is necessary to trigger "hasLayout" in Explorer Windows (except for 7)

div.container {
border: 1px solid #000000;
overflow: auto;
width: 100%
}

Source:http://www.quirksmode.org/css/clearing.html