var isNav, isIE, isMac

if (parseInt(navigator.appVersion) >= 4) {

       if (navigator.appName == "Netscape"){

               isNav = true

       }

       else {

       isIE = true

       }

}

isMac = (navigator.appVersion.indexOf("Mac") != -1);

if (isMac) 
{
	document.write("<LINK REL=STYLESHEET TYPE='text/css' HREF='mac.css'>");
}
else 

if (navigator.appName == "Netscape")
{
	document.write("<LINK REL=STYLESHEET TYPE='text/css' HREF='ns.css'>");
}

else {
	document.write("<LINK REL=STYLESHEET TYPE='text/css' HREF='ie.css'>");
}