<head>
  <style>
    body {
      width: 20em;
    }
  </style>
  <script src="page_action.js"></script>
</head>
<body>
  <h3>GWT Developer Plugin</h3>
  <div id='message'></div>
  <br/>
  <button id="updateConfiguration">Update Your Configuration</button>
  </p>
</body>