<html>
<body>
This page will attempt to load an iframe requiring basic auth from the
domain www.b.com using the same port that it loaded (since we assume www.b.com
is an alias for this same server).

<script>
var f = document.createElement("iframe");
f.src = "http://www.b.com:" + location.port + "/auth-basic/index.html";
document.body.appendChild(f);
</script>
</body>
</html>