function showLayer(layerName) {

	if(document.getElementById) {
	
		var onBG = document.getElementById("div" + layerName).style;
		var offBG = document.getElementById("div" + lastLayer).style;
		var newLayer = document.getElementById("tab" + layerName).style;
		var oldLayer = document.getElementById("tab" + lastLayer).style;
		if(layerName != lastLayer) {
						newLayer.backgroundColor = '#CCFFCC';
						newLayer.fontWeight = 'bold';
						newLayer.color = '#000000';
						newLayer.borderTopColor = '#33cc33';
						newLayer.borderTopWidth = '3px';
						oldLayer.backgroundColor = '#eeeeee';
						oldLayer.borderTopColor = '#cccccc';
						oldLayer.borderTopWidth = '3px';
						oldLayer.color = '#999999';
						oldLayer.fontWeight = 'normal';
						offBG.visibility = 'hidden';
						offBG.display = 'none';
						onBG.visibility = 'visible';	
						onBG.display = 'block';	
				}
		lastLayer = layerName;
	}
}