There has been a long standing discussion on the irregularities of the way the CSS properties ‘padding’ and ‘margin’ render themselves in IE as opposed to Firefox. I was recently stuck for a bit while adding block level elements like ‘ul’ and ‘form’ inside a floating ‘div’ element(which is yet another problem!). The first thing I did was to also float the block level item inside, in this case a form. I assigned float:right to it(the parent had float:left assigned to it). But then IE rendered it the way I wanted it to but Firefox slid the form about 100px to the right!
Padding the form on the right would render it correctly in FF but not in IE. So I used the FF specific -moz CSS extension, -moz-padding-end and that solved the problem.
Just a foot note: any CSS property preceded by a hyphen means that it is a browser specific property.
Here is the complete -moz CSS extensions reference.