Paul_o_b - 9:29 am on Aug 1, 2011 (gmt 0)
Very good explanation alt131:)
Yes my explanation was a little simplistic but the result is basically the same and the margin on the p becomes the margin on #bg as it collapses through the float above ignoring the empty clearer in Firefox.
All in all it looks like another plus for using overflow:hidden to clear floats (where possible) and avoid unexpected margin issues.:)