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

function dropdown_open()
{ 
    dropdown_canceltimer();
    dropdown_close();
    ddmenuitem = $(this).find('ul').css('visibility', 'visible');
}

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

function dropdown_timer()
{  
    closetimer = window.setTimeout(dropdown_close, timeout);
}

function dropdown_canceltimer()
{  
    if(closetimer)
    {  
        window.clearTimeout(closetimer);
        closetimer = null;
    }
}

$(document).ready(function(){  
        $('ul.nav > li').bind('mouseover', dropdown_open);
        $('ul.nav > li').bind('mouseout',  dropdown_timer);
        });

document.onclick = dropdown_close;