There was an interesting challenge — design a block with a non-fixed width (popup) that includes two other blocks with all the same unknown width, so that the indoor units lined up next to each other lined, and stretched the main unit. Here is the problem: if you specify both the inner blocks of float: left, they'll line up under each other. Actually no numeric parameters of all three units is unknown — therefore, to specify the width of anything is impossible.
Here is a simple example:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">div.popup {position: absolute;}div.popup > div {float: left;white-space: pre;}... Some unknown contentSome unknown content...
The result is one line under another, and it is necessary that they were in a line next to each other.