function showMenu( menu ) {
	var sub = document.getElementById(menu);
	sub.style.display = 'block';
	$('menu'+menu).setStyle('background-position', 'bottom');

}

function hideMenu( menu ) {
	var sub = document.getElementById(menu);
	sub.style.display = 'none';
	$('menu'+menu).setStyle('background-position', 'top');
}