bName = navigator.appName; 
bVer = parseInt(navigator.appVersion);
isMac = (navigator.appVersion.indexOf("Mac") != -1);

if(bName == "Netscape" && isMac==true) document.write('<link rel="stylesheet" href="scripts/macrubriek.css">');
else if(bName == "Microsoft Internet Explorer") document.write('<link rel="stylesheet" href="scripts/ierubriek.css">');
if(bName == "Netscape" && isMac==false) document.write('<link rel="stylesheet" href="scripts/nsrubriek.css">');