function toggleLayer(whichLayer)
{
  if (document.getElementById)
  {
    var style2 = document.getElementById(whichLayer).style;
//    alert("style " + style2.display);
    style2.display = style2.display=="block"? "":"block";
  }
  else if (document.all)
  {
// to suit old versions of MS IE
    var style2 = document.all[whichLayer].style;
    style2.display = style2.display=="block"? "":"block";
  }
  else if (document.layers)
  {
// this is the way Netscape 4 works
    var style2 = document.layers[whichLayer].style;
    style2.display = style2.display=="block"? "":"block";
  }
}