function hidden(id)
{
  if(document.getElementById)
    var elt = document.getElementById(id);
  else if(document.all)
    var elt = document.all[ id];
  else
    return;

  if (elt.style) {
    if (elt.style.display == 'none')
      elt.style.display = 'block';
    else
      elt.style.display = 'none';
  }
}