function changeImage(selected) {
  document.getElementById("featured").src = selected;
  
  var title_text = selected.title ? selected.title : "";
  
  var image_desc = document.getElementById("img-desc");
  image_desc.childNodes[0].nodeValue = title_text;
  
  return false;
}

function prepareGallery() {
  if (!document.getElementsByTagName ||
      !document.getElementById ||
      !document.getElementById("gallery-thumbs") ||
      !document.getElementById("featured")) return false;
      
  var links = document.getElementById("gallery-thumbs").getElementsByTagName("a");
  
  for ( var i = 0; i<links.length; i++ ) {
    
    if (links[i].className == "gallery_item") {
      links[i].onmouseover = function() {
        return changeImage(this);
      }
      links[i].onclick = function() {
        return changeImage(this);
      }
    }
    
    
  }
}

addLoadEvent(prepareGallery);