David’s Web Development Blog

Not sure why you’re getting wider margins or padding in IE6?  It’s a well-known issue with floating div elements, and it even has a specific name: the double margin (or double padding) bug.

The fix is simple.  Add this CSS rule to the floating Divs:
display: inline;

As an aside, it’s interesting to note that this fix doesn’t work if you’ve forgotten to add a unit value to your margin or padding.  For instance, if you’ve typed “padding: 10″ instead of “padding: 10px”, IE6 still doubles the 10 and presumes the units are in pixels.

Via http://www.jaymeblackmon.com/ie6-double-margin-bug-fix and                          http://www.positioniseverything.net/explorer/floatIndent.html