function displayShow(idName)
{
  var idObj = document.getElementById(idName);
  if (idObj == null)
    return;
  idObj.style.display = "block";
  return;
}
// ----------------------------------------------------------------------------
function displayHide(idName)
{
  var idObj = document.getElementById(idName);
  if (idObj == null)
    return;
  idObj.style.display = "none";
  return;
}
// ----------------------------------------------------------------------------
function classDisplayHide(className)
{
  var classObj = document.getElementsByClassName(className);
  for (i=0; i<classObj.length; i++) {
    classObj[i].style.display="none";
  }
}