<html>
  <head></head>
  <body></body>
  </html>

That's funny I thought it would be an empty response, but they explicitly hand-coded it like that.

Also -- offtopic but I think it's funny -- for conformance, you need a doctype and a (non-empty) title. So the above isn't valid, but this is:

  <!doctype html>
  <title>bleh</title>