anchor.diff:    var eventToBindTo = ('ontouchstart' in window) ? 'touchstart' : 'click';
   
     document.addEventListener('DOMContentLoaded', function(){
  -    var $front_back_container = document.querySelector('#f1_container');
  -
  -    document.querySelector('.flip-to-back').addEventListener(eventToBindTo, function(event){
  -      event.preventDefault();
  -      addClass($front_back_container, 'flipped');
  -    });
  +    var $front_back_container = document.querySelector('#f1_container'),
  +        $flip_to_back         = document.querySelector('.flip-to-back');
  +
  +    if ($flip_to_back) {
  +      $flip_to_back.addEventListener(eventToBindTo, function(event){
  +        event.preventDefault();
  +        addClass($front_back_container, 'flipped');
  +      });
  +    }
   
       document.querySelector('.flip-to-front').addEventListener(eventToBindTo, function(event){
         event.preventDefault();
  
positive.code:       text-shadow: 0px 1px 1px rgba(0,0,0,0.4);
        margin-bottom: 0;
      }
      input::-webkit-input-placeholder {
        color: #898989;
      }
  
negative.code:       display: block;
        font-size: 15px;
      }
      button, .button {
        text-align: center;
        background-image: -webkit-gradient(linear, 50% 0%, 50% 100%, color-stop(0%, #7ac0f8), color-stop(100%, #2e96e2));
        -webkit-box-shadow: black 0px 0px 2px 0px;
  