function show(divname)
{
  // set divname to be visible
  var obj = document.getElementById(divname);
  var deb = document.getElementById('debug');

  // set all other objects as invisible
  var par = obj.parentNode;

  // var counted = 0;
  for (var i=0; i < par.childNodes.length; ++i)
  {
    var iobj = par.childNodes[i];
    if (iobj.nodeName != "DIV")
       continue;
    // counted++;
    /* 
    deb.innerHTML += 'node ' + i + '/' + objparent.childNodes.length + ': ' + iobj.nodeType + '<br>';
    deb.innerHTML += 'iobj != obj  : ' +  iobj != obj + '<br>';  
    deb.innerHTML += 'typeof(iobj.style)  : ' +  typeof(iobj.style) + '<br>';  
    deb.innerHTML +='typeof(iobj.style.visibility)  : ' + typeof(iobj.style.visibility) + '<br>';  
    */
    iobj.style.visibility = 'hidden';
  }
  // deb.innerHTML = counted;
  obj.style.visibility = 'visible';
}