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. - Method Definitions

I was a little bit confused when I encoutered the HTTP status code 204, which states that the response MUST NOT include a message body. The HEAD method contains no body content as well. Should I use 204 instead of 200?

The answer is NO. GET method should always return HTTP status code of 200. Since HEAD method is idential to GET, it should return 200 as well. Just keep in mind that the cost of processing both HEAD and GET requests are almost the same.

My take on on HTTP methods and resources:

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+-----------------------------------------------------------+
| # | Request-URI              | Method         | RE  | RNE |
+-----------------------------------------------------------+
| 0 | GET    /resources        | list           | 200 | 200 |
| 1 | GET    /resources/entity | load/insert    | 200 | 404 |
|-----------------------------------------------------------|
| 2 | POST   /resources        | create         | 201 | 409 |
| 3 | POST   /resources/entity | N/A            | N/A | N/A |
|-----------------------------------------------------------|
| 4 | PUT    /resources        | (batch)        | 200 | 200 |
| 5 | PUT    /resources/entity | replace/save   | 204 | 201 |
|-----------------------------------------------------------|
| 6 | PATCH  /resources        | (batch)        | 200 | 200 |
| 7 | PATCH  /resources/entity | update         | 204 | 404 |
|-----------------------------------------------------------|
| 8 | DELETE /resources        | (batch)        | 200 | 200 |
| 9 | DELETE /resources/entity | remove/delete  | 204 | 404 |
+-----------------------------------------------------------+

Notes:

1. RE: resource exists
2. RNE: resource not exists
3. For batch request, whether resource/entity exists or not, the resulting HTTP
   status code is always 200, because the code is used to indicate the status
   of the operation. The actual status code of each entity is enclosed in the
   response array. When there are no matching entities, the response is an empty
   array, therefore, status code 204 is not used.
4. There are two situation, a new resource is being created, then the Location
   header must indicate the fully qualified resource URI.