As well as through the font checking utilities on this site, the perennial problem of font sizing methods acceptable for all browsers is discussed by Owen Briggs at his site. He supplies some handy cross-browser comparison screen shots.
Owen leans towards using percentages due to their compatability. I’ve recently started setting html {font-size:100%} then body {font-size:90%} and em units throughout the rest of the style sheet. Wondering whether it may be best to go back to using percentages only as it doesn’t seem to make much difference as long as the base font is set at 100%.