function menu_on(id) {
	for(i=1; i < 4; i++) {
		if((i != id) && (document.getElementById('menu'+String(i)) != undefined)) {
			document.getElementById('menu'+String(i)).style.visibility="hidden";
		}
	}
	if(document.getElementById('menu'+String(id)) != undefined) {
		document.getElementById('menu'+String(id)).style.visibility="visible";
	}
}



function menu_off(id) {
	if(document.getElementById('menu'+String(id)) != undefined) {
		document.getElementById('menu'+String(id)).style.visibility="hidden";
	}
}