function showSubMenu () {
	this.getElementsByTagName('ul')[0].style.visibility = 'visible';
}
function hideSubMenu () {
	this.getElementsByTagName('ul')[0].style.visibility = 'hidden';
}

function popup_menu (submenu) {
	for ( var i = 0; i < submenu.length; i++ ) {
		submenu[i].parentNode.onmouseover = showSubMenu;
		submenu[i].parentNode.onmouseout = hideSubMenu;
	}
}