var t;

function show_dd(menu_id) {
var menu = document.getElementById(menu_id);
menu.style.visibility = "visible";
clearTimeout(t);
}

function hide_dd(menu_id) {
var menu = document.getElementById(menu_id);
t=setTimeout("do_hide()",1000);
}

function do_hide() {
var menu = document.getElementById('services');
menu.style.visibility = "hidden";
}