<!--
Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
for details. All rights reserved. Use of this source code is governed by a
BSD-style license that can be found in the LICENSE file.
-->

<!DOCTYPE html>

<html>
  <head>
    <title>example</title>
    <style>
      section {
        display: none;
        width: 600px;
        height: 400px;
        border: solid 1px #888;
      }

      section.selected {
        display: block;
      }

      #warning {
        color: red;
   