browser_version= parseInt(navigator.appVersion);
browser_type = navigator.appName;
var win = (navigator.userAgent.toLowerCase().indexOf('win') != -1);
var mac = (navigator.userAgent.toLowerCase().indexOf('mac') != -1);

if (mac) {
  document.write("<link Rel='stylesheet' Type='text/css' HREF='/css/nick_mac.css'>");
}
else if (win && browser_type == "Netscape" && (browser_version >= 4)) {
  document.write("<link Rel='stylesheet' Type='text/css' HREF='/css/nick_ns.css'>");
}
else {
  document.write("<link Rel='stylesheet' Type='text/css' HREF='/css/nick.css'>");
}