function cssCheck() {
  var pc = (navigator.platform.indexOf('Win') != -1);
  var mac = (navigator.platform.indexOf('Mac') != -1);
  var linux = (mac != true && pc != true)? true: false;
  var n4 = (document.layers)? true : false;
  var ie = (document.all)? true : false;
    var opera = (navigator.userAgent.indexOf('Opera') != -1);
  stil = "";
  if (mac) {
    stil = "http://brokerage.onvista.sbroker.de/images/css/mac.css";
  } else {
      if ( (pc && n4) || (pc && opera) || linux ) {
          stil = "http://brokerage.onvista.sbroker.de/images/css/win_n_4.css";
      } else {
          stil = "http://brokerage.onvista.sbroker.de/images/css/win_ie.css";      }
  }
  return stil;
}