I'm out of the country, and so haven't got access to netscape at the moment.
Looking through your css, I notice that you often have something like
padding-top : 4pt;
padding-bottom : 0;
Here the bottom padding is not defined, and so I can imagine that mozilla has a different default then IE has (IE has px as default). Suggest cleaning that up and giving it another try.
If you use an editor which colourcodes your css (like source-edit) then these instances stand out.
Also check out htis tremendous css resource:
http://www.positioniseverything.net/