jQuery.fn.slideFadeToggle = function(speed, easing, callback) {
  return this.animate({opacity: 'toggle', height: 'toggle'}, speed,
easing, callback);
};

function showSub(subMenuIdentifier) {
	itemID = document.getElementById('submenu-' + subMenuIdentifier);
	itemFormatJQ = "#" + itemID;
	$(itemFormatJQ).slideFadeToggle('normal');
}