title: Content-Length header with HEAD requests?
body: <p>The <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.4" rel="noreferrer">http spec</a> says about the <code>HEAD</code> request:</p>
  
  <blockquote>
    <p>The HEAD method is identical to GET except that the server MUST NOT return a message-body in the response. The metainformation contained in the HTTP headers in response to a HEAD request SHOULD be identical to the information sent in response to a GET request.</p>
  </blockquote>
  
  <p>Should the response to a <code>HEAD</code> request contain a <code>Content-Length</code> header? Should it be the value which would be returned on a <code>GET</code> request, even if there is no response body? Or should the Content-Length be 0?</p>