browser = navigator.appName;
browserNum = parseInt(navigator.appVersion);
N4 = false;
N6 = false;
IE = false;
if ((browser == "Netscape") && (browserNum <5))
{ 
	// Netscape 4.x
	layerRef = "document.layers['";
	endLayerRef = "']";
	styleRef = "";
	N4 = true;
}
else if ((browser == "Netscape") && (browserNum >= 5))
{
	// Netscape 6
	layerRef = "document.getElementById('";
	styleRef = ".style";
	endLayerRef = "')";
	N6 = true;
}
else
{
	// Internet Explorer
	layerRef = "document.all['";
	endLayerRef = "']";
	styleRef = ".style";
	IE = true;
}
oldLayer = "none";
	function showLayer(layerName)
    {
	eval(layerRef + layerName + endLayerRef + styleRef + ".visibility = 'visible'");

    if (oldLayer != "none")
	{
		eval(layerRef + oldLayer + endLayerRef + styleRef + ".visibility = 'hidden'");
		
	}
 if (oldLayer == layerName)
	{
		oldLayer = "none";
	}
	else
	{
		oldLayer = layerName;
	}
    }
    function hideLayer(layerName)
{
	eval(layerRef + layerName + endLayerRef + styleRef + ".visibility = 'visible'");

if (oldLayer != "none")
	{
		eval(layerRef + oldLayer + endLayerRef + styleRef + ".visibility = 'hidden'");
	}
	
	if (oldLayer == layerName)
	{
		oldLayer = "none";
	}
	else
	{
		oldLayer = layerName;
	}
}	

function apri_finestra(indirizzo,nomefinestra,attributi) { 
    window.open(indirizzo,nomefinestra,attributi);
    }