function toggleLayer(myDiv, myURI)
{
   if (document.getElementById)
   {
      // this is the way the standards work
      var myStyle = document.getElementById(myDiv).style;
      myStyle.background = "url(" + myURI + ")";
   }
   else if (document.all)
   {
      // this is the way old msie versions work
      var myStyle = document.all[myDiv].style;
      myStyle.background = "url(" + myURI + ")";
   }
   else if (document.layers)
   {
      // this is the way nn4 works
      var myStyle = document.layers[myDiv].style;
      myStyle.background = "url(" + myURI + ")";
   }
}