What Content-Type should a 204 No Response use?

Question

When building a RESTful HTTP service, and a Response is given with a 204 No Content (e.g. after the Consumer issues a DELETE Request), what Content-Type should the Response

Answer 1

You have Content-Type when you have content and even then it's optional:

Any HTTP/1.1 message containing an entity-body SHOULD include a Content-Type header field defining the media type of that body.

(from RFC2616, §7.2.1, please note the use of SHOULD).

Since there is no content, then there is no reason to specify a Content-Type header.