function setActive(nr) {
  document.getElementById("menu"+nr).className = "choosen";
  if (nr == 1 || Math.floor(nr/10) == 1) document.getElementById("subnav1").style.display = "list-item";
  if (Math.floor(nr/10) == 2) document.getElementById("subnav2").style.display = "list-item";
  if (Math.floor(nr/10) == 3) document.getElementById("subnav3").style.display = "list-item";
  if (Math.floor(nr/10) == 4) document.getElementById("subnav4").style.display = "list-item";
}

function popFenster(url,breite,hoehe) {
  if(window.screen) 
  {
    var links = (screen.availWidth - breite - 10)/2;
    var oben = (screen.availHeight - hoehe - 30)/2;

    breite = parseInt(breite) + 18;
    hoehe = parseInt(hoehe) + 18;

    var neu = window.open(url,'Referenz','width='+ breite +',height='+ hoehe +',left='+ links +',top='+ oben );
    neu.focus();
  }
}