function change(elementId) {
  
  if(document.getElementById(elementId)) {

    // Sammle alle <ul> ab elementId ein
    var lis = document.getElementById(elementId).getElementsByTagName('ul');

    // Kehre Sichtbarkeit der 1. <ul>-Unterliste um (=lis[0])
    if(lis.length>0) {
      if (lis[0].style.display == "none") {
        lis[0].style.display = "block";
      }
      else {
        lis[0].style.display = "none";
      }
    }
  }
}

function showSub(elementId) {
  // z-Indizes von Navigation & Content tauschen
  document.getElementById("navigation2").style.zIndex = "6";
  document.getElementById("content").style.zIndex = "4";
  var lis = document.getElementById(elementId).getElementsByTagName('li');
  for (var i = 0; i < lis.length; i++) {
    if (lis[i].parentNode.id == elementId) {
      lis[i].style.display = "block";
      //lis[i].style.borderBottom = "1px solid white";
      var uls = lis[i].getElementsByTagName('ul');
      if (uls.length > 0) {
        uls[0].style.display = "none";
      }
    }
  }
}

function hideSub(elementId) {
  // z-Indizes von Navigation & Content zurücktauschen
  document.getElementById("navigation2").style.zIndex = "4";
  document.getElementById("content").style.zIndex = "6";
  var lis = document.getElementById(elementId).getElementsByTagName('li');
  for (var i = 0; i < lis.length; i++) {
    if (lis[i].parentNode.id == elementId) {
      if (lis[i].className != 'active' && lis[i].className != 'active2') {
        lis[i].style.display = "none";
      }
      var uls = lis[i].getElementsByTagName('ul');
      if (uls.length > 0) {
        uls[0].style.display = "block";
      }
    }
  }
}