var ie = navigator.appName == "Microsoft Internet Explorer";
  function dark(id)
  {
    if (ie)
      document.getElementById(id).style.filter="alpha(opacity=50)";
    else
      document.getElementById(id).style.opacity="0.5";
  }

  function light(id)
  {
    if (ie)
      document.getElementById(id).style.filter="alpha(opacity=100)";
    else
      document.getElementById(id).style.opacity="1";
  }