function showHide(elementId){
   var element = document.getElementById(elementId);
   if (!(element.style.display=='none' || element.style.visibility=='hidden'))
   {
      element.style.display = 'none';
      element.style.visibility = 'hidden';
   }
   else
   {
      element.style.display = 'block';
      element.style.visibility = 'visible';
   }
}