if ((navigator.userAgent.indexOf("Mac") != -1))
    document.write("<link rel='stylesheet' href='include/mac.css' type='text/css'>")
if (navigator.userAgent.indexOf('Win') != -1){
    if (navigator.appName.indexOf('Netscape') != -1) {
        document.write("<link rel='stylesheet' href='include/net.css' type='text/css'>")
        }
   else {
        document.write("<link rel='stylesheet' href='include/pc.css' type='text/css'>")
        }
    }