function showPic(whichpic) {
  if (!document.getElementById("imageMain")) return true;
  if (!document.getElementById("imageGallery")) return true;
  var source = whichpic.getAttribute("href");
  var placeholder = document.getElementById("imageMain");
  placeholder.setAttribute("src",source);
  var hook = whichpic.getAttribute("id") + "-on";
  var gallery = document.getElementById("imageGallery");
  gallery.className = hook;
  return false;
}
function prepareGallery() {
  if (!document.getElementsByTagName) return false;
  if (!document.getElementById) return false;
  if (!document.getElementById("imageGallery")) return false;
  var gallery = document.getElementById("imageGallery");
  var links = gallery.getElementsByTagName("a");
  for ( var i=0; i < links.length; i++) {
    links[i].onfocus = function() {
      return showPic(this);
    }
    links[i].onclick = function() {
      return showPic(this);
    }
  }
  return false;
}
addLoadEvent(prepareGallery);