var timeout    = 500;
var closetimer = 0;
var ddmenuitem = 0;

function ddmenu_open(){
	ddmenu_canceltimer();
	ddmenu_close();
	ddmenuitem = $(this).find('ul').css('visibility', 'visible');
}

function ddmenu_close(){ 
	if(ddmenuitem) ddmenuitem.css('visibility', 'hidden');
}

function ddmenu_timer(){
	closetimer = window.setTimeout(ddmenu_close, timeout);
}

function ddmenu_canceltimer(){  
	if(closetimer){  
		window.clearTimeout(closetimer);
		closetimer = null;
	}
}
$(function(){
	$('#nav ul li > ul').parent('li').hover(ddmenu_open,ddmenu_timer);
});