http response

• The HTTP version is in the same format as in the request line, "HTTP/x.x".
• The status code is meant to be computer-readable; the reason phrase is meant to be human-readable, and may vary.
• The status code is a three-digit integer, and the first digit identifies the general category of response:
  • 1xx indicates an informational message only
  • 2xx indicates success of some kind
  • 3xx redirects the client to another URL
  • 4xx indicates an error on the client's part
  • 5xx indicates an error on the server's part