Safari/Firefox on a Mac not displaying things right!

I’ve set up my wordpress blog pretty much the way i want it on a pc, everything is looking fine, but when i view the site on a mac, either in Safari or Firefox, things like links are’nt underlined, or the body text is displayed in Times when i want it in Helvetica/Arial. I know that correcting the display type from Times to Arial in Safari works, but is there a way to have it displayed automatically? any help is appreciated.