var timeout    = 1000;
var closetimer = 0;
var ddmenuitem = 0;
function navigation_open()
{  navigation_canceltimer();
   navigation_close();
   ddmenuitem = $(this).find('div.submenu').css('visibility', 'visible');}

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

function navigation_timer()
{  closetimer = window.setTimeout(navigation_close, timeout);}

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

$(document).ready(function(){  
  $('#navigation td').bind('mouseover', navigation_open)
  $('#navigation td').bind('mouseout',  navigation_timer)
});

document.onclick = navigation_close;