2xx - OK
The request has succeeded, the requested resource is available and may be displayed. This is the standard response in a successful request.
The client request has resulted in the resource being created, on receipt of a POST of variables that define how the resource is to be created. A 202 status may be issued while creation of the resource takes place.
The client request has been accepted, this request may or may not be acted on depending on the specifics of the request, a further status will be issued.
203 (Non-Authoritative Information)
This status indicates that the resource is available but not from the original source, in essence this is a "200" status but without certainty of the resource source.
204 (No Content)
The request has been successful but there is no additional content that needs to be sent. If the client is a browser for example no changes need to be made to the displayed output. This status is primarily to allow additional information to be sent to the server without interrupting the client view, for example this would allow additional data to be sent to a script. This status show never include a message body - as of course there should not be any content to make up the message body.
205 (Reset Content)
The request has been successful and the client view should now be reset. For example, form data has been sent (and received) - the client should now reset (or move on from) the form so that the form is no longer displayed.
206 (Partial Content)
The client has a copy of the relevant resource in its cache. However, there is a discrepancy in the "last modified date" and therefore the client has requested additional parts to the resource. Essentially the request made is: "if the resource is unchanged, please send the part (or parts) that I am missing; otherwise, send the entire resource". This status indicated that the request was successful.