diff --git a/prototype/UI/index.html b/prototype/UI/index.html
index 8ed271b58..1bddcfabb 100644
--- a/prototype/UI/index.html
+++ b/prototype/UI/index.html
@@ -82,6 +82,8 @@
     </script>
   </head>
   <body>
+    <div id="before"></div>
+    <div id="after"></div>
     <div id="diff"></div>
     <script type="text/javascript">
     loadJSON('diff.json', function (json) {
