// Stylesheet einbinden
if (document.all) {                  // IE4
document.write("<link rel='stylesheet' type='text/css' href='/win.css'>");
} else {
  if (navigator.appVersion.indexOf("Win") != -1) {  // Windows
    document.write("<link rel='stylesheet' type='text/css' href='/win_net.css'>");
  } else {  // Linux, Mac
    document.write("<link rel='stylesheet' type='text/css' href='/other.css'>");
  }
}