static/error_504.html

<html>
  <head>
    <title>Error 504 - Application Not Responding</title>
    <style>
      body { background-color: #dedede; margin: 0; }
      h1 { padding: 280px 0 0 0; margin: 0; text-align: center; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 24px; font-weight: normal; }
      h2 { padding: 5px 0 0 0; margin: 0; text-align: center; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; color: #999; font-weight: normal; }
    </style>
  </head>
  <body>
    <center><div style="width: 530px; height: 434px; background-image: url(http://static.dotcloud.com/proxy/warning.png); margin: 25px auto;">
      <h1>
        Application Not Responding
      </h1>
      <h2>
        Please try again in a few moments.
      </h2>
    </div></center>
  </body>
</html>