function toggle_selects()
{
   var s=document.getElementsByTagName('select');
   for(var i=0;i<s.length;i++)
   {
       v=s[i].style.visibility;
       s[i].style.visibility=(v=='hidden'?'visible':'hidden');
   }
}

function overlay_show()
{
  toggle_selects();
  
  document.getElementById('overlay').style.display='block';
  document.getElementById('login_box').style.display='block';
}

function overlay_hide()
{
  toggle_selects();
  
  document.getElementById('overlay').style.display='none';
  document.getElementById('login_box').style.display='none';
}