function toggleDisplay(id) {
  var displayMode;
  if (document.layers) {
    displayMode = (document.layers[id].display == 'none') ? 'block' : 'none';
    document.layers[id].display = displayMode;
  } else if (document.all) {
    // IE (5.0) case.
    displayMode = (document.all[id].style.display == 'none') ? 'block' : 'none';
    document.all[id].style.display = displayMode;
  } else if (document.getElementById) {
    // Netscape (6/7.1) case.
    displayMode = (document.getElementById(id).style.display == 'none') ? 'block' : 'none';
    document.getElementById(id).style.display = displayMode;
  }
}