All your font sizes seem to be in px, mainly 12px; and I find that it looks the same in IE7, Firefox, Opera (all on Windows) but Safari for Windows shows the text slightly smaller and thicker, it almost looks bold.
I find this with my sites too and I don't know of a cure. If they all have a font size stated there isn't anything else I can think of to solve it, except:
If you could set a javascript sniffer for Safari then you could set a stylesheet just for Safari and set the font-weight at a lower number but I don't know the javascript for that.
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.