<A> width in Mozilla
First of all Moz is correct in its render. IE compensates and looks ok.
For A.menuItem you put width: 100%; Well the width will be the length of the text as that is the link. add some more text to one of the links and see what happens in Moz.
to fix get rid of width: 100%; and put in display: block; instead.
on the size - add height: 20px; and now moz and IE have same.
BTW you should also add a correct Doc Type. Becasue you do not have a Doc Type all Browsers will render in quirky mode, and it will be difficulkt to get them to match.