function absLeft(el)
{
  return (el.offsetParent) ? el.offsetLeft+absLeft(el.offsetParent) : el.offsetLeft;
}

function absTop(el)
{
  return (el.offsetParent) ? el.offsetTop+absTop(el.offsetParent) : el.offsetTop;
}

function alleweg()
{
  //Layer auf hidden stellen
  document.getElementById("idAutohaus").style.visibility = "hidden";
  document.getElementById("idModelle").style.visibility = "hidden";
  document.getElementById("idNeuigkeiten").style.visibility = "hidden";
}

function oeffnemenu(refer, menuname)
{
  var x = absLeft(refer);
  var y = absTop(refer);

  alleweg();

  //Layer anzeigen
  document.getElementById(menuname).style.left = x + 'px';
  document.getElementById(menuname).style.top = y + 15 + 'px';
  document.getElementById(menuname).style.visibility = "visible";
}