When you center things in explorer it acts like there was a vertical scrollbar even if there ain't any.
This was done to prevent recentering in case dynamic content makes a scrollbar appear.
Problem is that our beloved menu centers itself CORRECTLY, without the "fake scrollbar" trick.
This makes a correctly centered menu in explorer fail to align on other browsers(in my case Mozilla).
To correct the behaviour(or to break it the MS way

ww=_d.body.clientWidth;
into
ww=_d.body.clientWidth-15;
Cya!