function getLayerRef (id, document) {
  if (!document)
    document = window.document;
  if (document.layers) {
    for (var l = 0; l < document.layers.length; l++)
      if (document.layers[l].id == id)
        return document.layers[l];
    for (var l = 0; l < document.layers.length; l++) {
      var result = getLayerRef(id, document.layers[l].document);
      if (result)
        return result;
    }
    return null;
  }
  else if (document.all) {
    return document.all[id];
  }
  else if (document.getElementById) {
    return document.getElementById(id);
  }
}
function setVisibility(objLayer, visible) {
  if(document.layers){
    objLayer.visibility  = 
        (visible == true) ? 'show' : 'hide';
  } else {
    objLayer.style.visibility = 
        (visible == true) ? 'visible' : 'hidden';
  }
}