function toggleLayer(whichLayer)
{  
	var elem;  
	var 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';
}