Off Topic:
Strange, even zooming that page I don’t get the effect you mentioned.
EDIT: sorry, yes I do. I must have gone to a zoom % at which the effect didn’t happen, as other zoom levels it does. D’oh!
I was disappointed when Firefox was set to zoom the whole page (rather than text only) by default. Kinda ruins the point of flexible, em-based layouts IMHO. Anyway, I set FF to View > Zoom > Zoom text only.