Wow, we just upgraded to 4.2. On Firefox 3.0 the font is SOO small, like 6pt or something. Why the crazy small font size? To fix this, go into global.css and find and replace all places where it says smaller and change it to small. Not sure why the developers thought itty bitty fonts were a good idea.
Actually, that's the same font size that we always used, but it is smaller on newer browsers. We noticed this in development, but no one felt strongly about changing it at the time. I changed css per your suggestion and it looks ok to me, maybe I'll run it a bit and commit it if no one objects...