Alright, to get the fonts to work in FireFox you must have negative values on all fonts, so instead of (positive) 12 it's got to be -8 (12 and -8 give you the same result in the preview), but if you set all the fonts to -8 then in IE the fonts on buttons (such as "Search" at google.com) are half the size of what they should be, so instead of 12px they're 6px.
Not only that, but when the fonts have negative settings they also screw up in GIMP.
Does anyone know how to fix this problem?