function opennav (which)
{
  if (!document.getElementById)
    return;

  var ul = document.getElementById('nav' + which);
  if (!ul)
    return;

  ul.style.display = 'block';
}

function closenav (which)
{
  if (!document.getElementById)
    return;

  var ul = document.getElementById('nav' + which);
  if (!ul)
    return;

  ul.style.display = 'none';
}