I’m at home today working on a new WordPress site… just came across the glorious IE Float/Margin bug. Thankfully there are a couple of workarounds, one involving putting an extra Div around the troublesome ones, the other involving a harmless display: inline attribute.
I also note that when wrangling with a CSS file and WordPress, continually tweaking, uploading the tweaked file, then re-loading the browser page, Firefox handles it fine and refreshes completely. IE doesn’t; sometimes it’ll only do a partial refresh, and chokes on something, which in my case means my navigation bar disappearing until I re-load via a link. Very odd.