var rCurrentLayer = "";

isNS4 = (document.layers) ? true : false;
isIE4 = (document.all && !document.getElementById) ? true : false;
isIE5 = (document.all && document.getElementById) ? true : false;
isNS6 = (!document.all && document.getElementById) ? true : false;


function revealLayer(layerName) {
	//if another layer is currently visible, hide it
	if(rCurrentLayer != "") {
		toggleLayer(rCurrentLayer, "hidden");
	}
	//if no layer is visible, or a layer other than the currentLayer is visible
	if(rCurrentLayer == "" || rCurrentLayer != layerName) {
		//reveal the requested layer
		toggleLayer(layerName, "visible");
		//assign requested layer to currentLayer
		rCurrentLayer = layerName;
	}
	//if the currentLayer is already on, hide it.
	else {
		toggleLayer(layerName, "hidden");
		//assign requested layer to currentLayer
		rCurrentLayer = "";
	}
}