One method I've used from time to time to get around the
problem of Macs and PCs having different ideas about the size
of a particular point size is to specify the font height in pixels:
p {
font-family: Verdana, Helvetica, Arial, sans-serif;
font-size: 12px;
color: #ffffff;
}
Of course, this completly destroys the whole relative font
size thing, but hey, it's an imperfect world.
The ideal solution would use a browser/platform detection
script to link in a stylesheet specific for that particular
browser/platform's idiosyncrasies. Ugly. Maybe one of these
days all browsers will support CSS properly. I don't have high
hopes for this, however.