function showLayer(layerid) {
	layer = document.getElementById(layerid);
	layer.style.visibility = "visible";
}

function hideLayer(layerid) {
	layer = document.getElementById(layerid);
	layer.style.visibility = "hidden";
}

function showTwoLayer(layerID_01, layerID_02) {
	showLayer(layerID_01);
	showLayer(layerID_02);
}

function hideTwoLayer(layerID_01, layerID_02) {
	hideLayer(layerID_01);
	hideLayer(layerID_02);
}