function keyCheck() {
    if(event.keyCode == 13) {
      code();
    }
  }
  function code() {
    var realcode = new Array("xfgb");
    var code     = document.getElementById('codeFeld').value;
    var target   = code.substr(0,4);
    var laenge = code.length;
    if (in_array(target,realcode) && laenge>4) {
      var userId = code.substr(4,laenge);
      document.location.href = 'http://www.systemtechnik-lau.de/' + target + '.0.html?userId=' + userId;
    }
    else {
      alert('Leider ist der Code ungültig !');
    }
  }

   function in_array(mVal, aArray) {
           for (sIndex in aArray) {
                if (aArray[sIndex] == mVal) {
                     return true;
                }
           }
           return false;
   }