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

function mainnavbar_open()
{  mainnavbar_canceltimer();
   mainnavbar_close();
   ddmenuitem = $(this).find('ul').css('visibility', 'visible');}

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

function mainnavbar_timer()
{  closetimer = window.setTimeout(mainnavbar_close, timeout);}

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

$(document).ready(function()
{  $('#mainnavbar > li').bind('mouseover', mainnavbar_open)
   $('#mainnavbar > li').bind('mouseout',  mainnavbar_timer)});

document.onclick = mainnavbar_close;