Use the Theme Font & Size Changer add-on to change the font size.

Thank you so much!!!

This happened to me, too today when I turned on the computer. I did see it saying it was installing updates, but not sure if it was from Windows or Firefox/mozilla. I have Windows 7. All the font on the webpages themselves are fine. Also right click font is tiny now, too. And the font style itself is different.

UPDATE: Changed my display fonts to 135% from 125% and that helped but it still has a problem. The drop down dialog boxes are in basic grey, that says to me something crashed. I think there was a major surcharge last night as my plugged in phone was haywire this morning, too. I do have a surcharge protector on my computer, though.

I rebooted and it seems better now. I'd like to delete this post but see no way to do so.