browser = navigator.appName;
os = navigator.platform;
ie = "Microsoft Internet Explorer";
netscape = "Netscape";
mac = "MacPPC"

if(browser == netscape && os != mac) {
   document.write('<link rel=stylesheet type="text/css" href="http://expn.go.com/insertfiles/tube/css/tube_nn.css">');
} else if(browser == netscape && os == mac) {
   document.write('<link rel=stylesheet type="text/css" href="http://expn.go.com/insertfiles/tube/css/tube_nn_mac.css">');
} else if(browser == ie && os == mac) {
   document.write('<link rel=stylesheet type="text/css" href="http://expn.go.com/insertfiles/tube/css/tube_ie_mac.css">');
} else {
   document.write('<link rel=stylesheet type="text/css" href="http://expn.go.com/insertfiles/tube/css/tube.css">');
}