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

function menu_open(){  
    menu_canceltimer();
    menu_close();
    ddmenuitem = $(this).find('ul').css('visibility', 'visible');
}

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

function menu_timer(){  
    closetimer = window.setTimeout(menu_close, timeout);
}

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

$(document).ready(function(){  
    $('#menu > li').bind('mouseover', menu_open)
    $('#menu > li').bind('mouseout',  menu_timer)
});

document.onclick = menu_close;