In FF, frontpage grid (3x3) looks great.
In IE8, frontpage turns into a single column.
Vidyut Kale answers:
I see that you have separate stylesheets that for IE7 and IE6, not for IE8.
I don't have an IE8 to test, so I can't say for sure, but to me it looks like the margins are being rendered in whatever 'quirks-mode' is called when it renders like IE7 rather than standards compliant. So the box model is following the old IE thing.
To troubleshoot, try adding the same stylesheet that is for IE7 for IE8 as well, and see if that fixes it. Or you'll have to code a fresh one.