function on ()
{
  if (document.getElementById)
  {
    document.getElementById("bild").style.visibility = "visible";
    document.getElementById("text").style.visibility = "hidden";
  }
}

function off ()
{
  if (document.getElementById)
  {
    document.getElementById("bild").style.visibility = "hidden";
    document.getElementById("text").style.visibility = "visible";
  }
}