Bug Fix: IE Double Margin Float Bug
http://www.cssnewbie.com/double-margin-float-bug/

Glazebrook, Rob L.
CSSnewbie
2008

Abstract:

The double-margin float bug -- an Internet Explorer-exclusive bug wherein an element that is floated – and given a margin in the same direction as the float – ends up with twice the specified margin size -- has been a source of irritation for CSS-loving web designers for years. While an easy (if mysterious) fix has been known for quite some time now, it occurs to me that perhaps not everyone knows about it. So I thought it couldn’t hurt to toss another explanation out there.