function changeImage(mychoice) {
  document.getElementById("fullimage").src = mychoice;
  
  var title_text = mychoice.getAttribute("title") ? mychoice.getAttribute("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") ||
      !document.getElementById("fullimage")) return false;
      
  var links = document.getElementById("gallery").getElementsByTagName("a");
  
  for ( var i = 0; i<links.length; i++ ) {
    links[i].onmouseover = function() {
      return changeImage(this);
    }
    links[i].onclick = function() {
      return changeImage(this);
    }
  }
}

window.onload = prepareGallery();