function menu_activate(obj, index, arr) {
	obj.className = 'item_active';
	for(i in arr) {
		var item = document.getElementById(arr[i]);
		item.className = 'hidden';
 	}
 	var menu_item = document.getElementById(arr[index]);
 	menu_item.className = '';
}

function menu_inactivate(obj) {
	obj.className = 'item';
}