function posTop() { return typeof window.pageYOffset != 'undefined' ?
  window.pageYOffset : document.documentElement && document.documentElement.scrollTop ?
  document.documentElement.scrollTop : document.body.scrollTop ?
  document.body.scrollTop : 0; }

function enlargethumb(name, jpg, dir, label) {
  if (!dir) dir = 'images';
  // name is the name of the javascript large image object.
  // jpg is the filename of the small image, w/o the '.jpg'
  var mywrite = "<a href=\"#\" onMouseOver=\"document." + name 
    + ".style.top = posTop() + 50 +  \'px\'; document." + name 
    + ".style.visibility=\'visible\'; \" onMouseOut=\"document." + name 
    + ".style.visibility=\'hidden\'; \"  >  <img src=\'" + dir + "/" + jpg 
    + ".jpg\'>  </a>";
  if (label) mywrite += label + '<br />';
  else mywrite += '<br />';
  document.write(mywrite); 
}