var active = -1;

function menu_activate ( item ) {
	if ( active >= 0 )
		menu_deactivate ( active );

	var submenuItem = document.getElementById("submenu_" + item);
	if ( ! submenuItem)
		return;
		
	submenuItem.style.display = "block";
	
	active = item;
}

function menu_deactivate ( item ) {
	var submenuItem = document.getElementById("submenu_" + item);
	if ( ! submenuItem)
		return;
	
	submenuItem.style.display = "none";
}