penders - 6:41 pm on Jun 30, 2011 (gmt 0)
It relies on the basic fact that a floated container will contain any children floated within it.
Presumably this is the same principle that a parent container with overflow:hidden will also contain floated children?
Although I think @jonasisme is a bit stuck if using a DL. A parent container around each (DT DD DD) block would certainly invalidate the HTML.