Last week I had a weird problem. While developing a page for a project where I needed two tables in a nested div. I stumbled upon the fact the a <br /> is fucking up the layout. This only seems to be a problem using google chrome on ms windows xp a.f.a.i.k. where it stores the lower table right of the content div where I wanted it.
The solution? A plain clear: both; in the lower table seems to solve it.