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';
	
}