<script>
function parseHttpHeaders(httpHeaders) {
    return httpHeaders.split("\n")
        .map(x=>x.split(/: */,2))
        .filter(x=>x[0])
        .reduce((ac, x)=>{ac[x[0]] = x[1];return ac;}, {});
}

var req = new XMLHttpRequest();
req.open('HEAD', document.location, false);
req.send(null);

var headers = parseHttpHeaders(req.getAllResponseHeaders());
</script>

<center>
  <h1>Whoops!</h1>
  <h3><script>document.write(req.status);</script></h3>
  The server can not find the requested resource. In the browser, this means the URL is not recognized.</br></br>
  Request-Id: <script>document.write(headers["x-hcdn-request-id"]);</script>
</center>