In the past, I would have problems with container divs not displaying properly, having zero size. So my container div would be displayed as a line, and the rest of my content would overflow out …. Urrgh..
So I would usually put <div style=“clear: both; height: 1%;”></div>
But now, thanks to http://www.quirksmode.org/css/clearing.html, I have discovered the wonders of overflow: auto. :)