The official documentation has moved to http://docs.couchdb.org — The transition is not 100% complete, but http://docs.couchdb.org should be seen as having the latest info. In some cases, the wiki still has some more or older info on certain topics inside CouchDB.
A list of HTTP statuses used by CouchDB and their respective meanings.
See also the official documentation for this topic.
200 - OK
Request completed successfully.
201 - Created
Document created successfully.
202 - Accepted
Request for database compaction completed successfully.
304 - Not Modified
Etag not modified since last update.
400 - Bad Request
Request given is not valid in some way.
404 - Not Found
Such as a request via the HttpDocumentApi for a document which doesn't exist.
405 - Resource Not Allowed
Request was accessing a non-existent URL. For example, if you have a malformed URL, or are using a third party library that is targeting a different version of CouchDB.
409 - Conflict
Request resulted in an update conflict.
412 - Precondition Failed
Request attempted to created database which already exists.
500 - Internal Server Error
Request contained invalid JSON, probably happens in other cases too.
As you can see, this document is incomplete, please update.