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

function dropdownmenu_open()
{  dropdownmenu_canceltimer();
   dropdownmenu_close();
   ddmenuitem = $(this).find('ul').css('visibility', 'visible');}

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

function dropdownmenu_timer()
{  closetimer = window.setTimeout(dropdownmenu_close, timeout);}

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

$(document).ready(function()
{  $('#dropdownmenu > li').bind('mouseover', dropdownmenu_open)
   $('#dropdownmenu > li').bind('mouseout',  dropdownmenu_timer)});

document.onclick = dropdownmenu_close;