browser = navigator.appName;
		browserNum = parseInt(navigator.appVersion);
		
		if ((browser == "Netscape") && (browserNum < 5))
		{
			// Netscape 4.x
			layerRef = "document.layers['";
			endLayerRef = "']";
			styleRef = "";
		}
		else if ((browser == "Netscape") && (browserNum >= 5))
		{
			// Netscape 6
			layerRef = "document.getElementById('";
			styleRef = ".style";
			endLayerRef = "')";
		}
		else
		{
			// Internet Explorer
			layerRef = "document.all['";
			endLayerRef = "']";
			styleRef = ".style";
		}
		
		// create way to remember which layer is visible
		oldLayer = "none";
		
		function showMenu(layerName)
		{
			// show the layer the user wants to see
			eval(layerRef + layerName + endLayerRef + styleRef + ".visibility = 'visible'");
			
			// hide other window
			if (oldLayer != "none")
			{
				eval(layerRef + oldLayer + endLayerRef + styleRef + ".visibility = 'hidden'");
			}
			
			if (oldLayer == layerName)
			{
				oldLayer = "none";
			}
			else
			{
				oldLayer = layerName;
			}
			
		}