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