function toggleLayer(whichLayer) {
  if (document.getElementById) {
    // this is the way the standards work
    var style2 = document.getElementById(whichLayer).style;
    style2.display = style2.display? "":"block";
  }
  else if (document.all) {
    // this is the way old msie versions work
    var style2 = document.all[whichLayer].style;
    style2.display = style2.display? "":"block";
  }
  else if (document.layers) {
    // this is the way nn4 works
    var style2 = document.layers[whichLayer].style;
    style2.display = style2.display? "":"block";
  }
}