function toggleLayer(whichLayer){
      if (document.getElementById){
        // this is the way the standards work
        var element = document.getElementById(whichLayer)
        var style2 = element.style;
        style2.display = style2.display ? "":"none";
      }else if (document.all){
        // this is the way old msie versions work
        var element = document.all[whichLayer]
        var style2 = element.style;
        style2.display = style2.display? "":"block";
      }else if (document.layers){
        // this is the way nn4 works
        var element = document.layers[whichLayer];
        var style2 = element.style;
        style2.display = style2.display? "":"block";
      }
}