Because I had a bit of data and, as I said previously, this is a dirty survey. I looked at the Alexa top 500 Web sites. More surprises.
325 HTTP/1.1 200 OK
65 HTTP/1.1 301 Moved Permanently
33 HTTP/1.1 302 Found
22 HTTP/1.0 200 OK
16 HTTP/1.1 302 Moved Temporarily
4 HTTP/1.1 405 MethodNotAllowed
4 HTTP/1.1 404 Not Found
3 HTTP/1.0 301 Moved Permanently
2 HTTP/1.1 500 Internal Server Error
2 HTTP/1.1 406 Not Acceptable
2 HTTP/1.1 405 Method Not Allowed
2 HTTP/1.1 403 Forbidden
2 HTTP/1.1 302 Object moved
2 HTTP/1.1 204 No Content
1 HTTP/1.1 405 Request method 'HEAD' not supported
1 HTTP/1.1 400 Bad Request
1 HTTP/1.1 303 See Other
1 HTTP/1.1 301 Moved
1 HTTP/1.1 200 Ok
1 HTTP/1.0 503 no backend
1 HTTP/1.0 403 Forbidden
1 HTTP/1.0 302 Found
Now I really want to look deeper and more properly to these data. Little project next week?
PS: Note that the reason phrase (the part after the 3 digits code) is optional. User agents do not have to rely on it. It is a message for humans to make the response more human friendly.