function toggleLayer( whichLayer )
{
	var elem, vis;

	if(document.getElementById ) // standards
		elem = document.getElementById( whichLayer );
	else if(document.all ) // msie versions
		elem = document.all[whichLayer];
	else if(document.layers ) // nn4
		elem = document.layers[whichLayer];
		
	vis = elem.style;
  
	// if the style.display value is blank we try to figure it out here
	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';
}