the "Visit your mobile Plurk page" at the bottom of this page is one example. It's on two lines instead of one.

yup same here...isn't ff3 totally (well, more-so than others) standards compliant though? is it the pages' fault?

I think it is the pages' "fault". However that still doesn't fix it so everythign I see isnt all screwed up.

FF3, just like 2, has clearing issues when you use floating elements. Been trying to find a good fix.