[Aetae]

var comment = (function createCurrentURLComment(window){
  var document = window.document,
      location = window.location, 
      html = document.documentElement;
  
  var comment = html.insertBefore( 
    document.createComment(location.href), 
    html.firstChild
  );
  
  window.addEventListener('popstate', function(){
    comment.data = location.href;
  }, false);
  
  return comment
}(window));