// JavaScript Document
function toggleLayer( whichLayer ){  
var elem, vis;  if( document.getElementById ) 
   elem = document.getElementById( whichLayer );  
   else if( document.all )     
   elem = document.all[whichLayer];  else if( document.layers ) 
   elem = document.layers[whichLayer];
   vis = elem.style;
   if(vis.display == '' && elem.offsetWidth!=undefined && elem.offsetHeight!=undefined) vis.display = (elem.offsetWidth!=0 && elem.offsetHeight!=0)?'block':'none';  
   vis.display = (vis.display == '' || vis.display=='block')?'none':'block';
}