In my IE7 the menu buttons are in line with the nav bar but in Firefox they are just below.
Since the menu buttons are in the ul tags, I put in an extra style:-
#nav ul {margin-top:0px;}
I expected to have to put in a negative margin-top to raise them up, assuming that they were already at 0 margin-top, but that wasn't the case; they moved into the nav bar with 0 margin-top. They still stay in the nav bar in IE7 so for some reason FF must have been applying a margin-top while IE7 did not.
If IE7 buttons had moved out of position while FF buttons moved into position then a conditional comment for IE7 would have been required to reverse IE7 but on my PC it isn't necessary.
.
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.