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

function nav_drop_open()
{  nav_drop_canceltimer();
   nav_drop_close();
   ddmenuitem = $(this).find('ul').css('visibility', 'visible');}

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

function nav_drop_timer()
{  closetimer = window.setTimeout(nav_drop_close, timeout);}

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

$(document).ready(function()
{  $('#nav_drop > li').bind('mouseover', nav_drop_open)
   $('#nav_drop > li').bind('mouseout',  nav_drop_timer)});

document.onclick = nav_drop_close;