shells/browser/shared/popups/enabled.html

<script src="shared.js"></script>
<style>
  html,
  body {
    font-size: 14px;
    min-width: 460px;
    min-height: 39px;
  }

  body {
    margin: 8px;
  }

  hr {
    width: 100%;
  }
</style>
<p>
  <b>This page is using Relay. &#x2705;</b>
  <br />
  Open the developer tools, and the Relay tab will appear to the right.
</p>