Legend bug in Firefox

The first fieldset below is not wrapped in a div, but the legend element should display the same as the one in the second fieldset.

I believe the "bug" is related to the "top" property. Here, I am using "margin-top" instead of "top" (top:0; is for Internet Explorer only) and things seem to be working fine...

  1. 1.

    This legend is styled with an additional span
  2. 2.

    This legend is styled with an additional span

    This fieldset has an additional <div> around it.