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';
}