var ns=true;
var ie=true;
var browser = navigator.appName;
var agent = navigator.userAgent; 
var IE4 = (document.all) ? true : false;
var NS4 = (document.layers) ? true : false;
var IEStyles = "<link rel='stylesheet' href='/style.css' type='text/css'>"
var NSStyles = "<link rel='stylesheet' href='/stylen.css' type='text/css'>";
var MacIEStyles = "<link rel='stylesheet' href='/styleme.css' type='text/css'>"
var MacNSStyles = "<link rel='stylesheet' href='/stylemn.css' type='text/css'>";

if (agent.indexOf("Win") >= 0) { 
if (browser == 'Netscape') ie=false; else ns = false; 
if (ie) document.write(IEStyles); else document.write(NSStyles);
}

else if (agent.indexOf("Mac") >= 0) {
if (browser == 'Netscape') ie=false; else ns = false; 
if (ie) document.write(MacIEStyles); else document.write(MacNSStyles);
}