window.onload = createGallery;

function createGallery() {
  for (var i = 0; i < document.links.length; i++) {
    if (document.links[i].className == "galleryImage") {
      document.links[i].onclick = newWindow;
    }      
  }
}

function newWindow() {
  var newWindow = window.open(this.href,"imgDisp","resizable=no,width=600,height=450,scrollbars=yes");
  return false;
}