function showLayer( whichLayer ){
	var elem, vis;
	elem = document.getElementById( whichLayer );
	vis = elem.style;
	vis.display = 'block';
}

function hideLayer( whichLayer ){
	var elem, vis;
	elem = document.getElementById( whichLayer );
	vis = elem.style;
	vis.display = 'none';
}

function toggleLayer( whichLayer ){
	var elem, vis;
	elem = document.getElementById( 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';
}