function showPic(whichpic) {
  if (!document.getElementById("placeholder")) return true;
  var source = whichpic.getAttribute("href");
  var placeholder = document.getElementById("placeholder");
  placeholder.setAttribute("src",source);
  
  var end = source.indexOf(".jpg");  
  var start = end -1;
  
  var oldsource = source.substring(start,end);

  if (whichpic.getAttribute("id") == "back") {
	var down = Number(oldsource) -1;
  } else {
	var down = Number(oldsource) -1;
  }
  var up = down +2;
  
  if (down < 1) {down = max};
  if (up > max) {up = 1}
  
  var newback = source.substring(0,start) + down + ".jpg";
  var newforward = source.substring(0,start) + up + ".jpg";
  document.getElementById("back").setAttribute("href",newback);
  document.getElementById("forward").setAttribute("href",newforward);
  
  return false;
}


function prepareGallery() {
  if (!document.getElementsByTagName) return false;
  if (!document.getElementById) return false;
  if (!document.getElementById("gallerynav")) return false;
  
  var gallery = document.getElementById("gallerynav");
  var links = gallery.getElementsByTagName("a");
  for ( var i=0; i < links.length; i++) {
    links[i].onclick = function() {
      return showPic(this);
    }
  }
}

addLoadEvent(prepareGallery);