http://www.rfc-editor.org/rfc/rfc2310.txt
RFC 2310: The Safe Response Header Field, K. Holtman1998-04-01T23:00:00-00:00This document defines a HTTP response header field called Safe, which can be used to indicate that repeating a HTTP request is safe. This memo defines an Experimental Protocol for the Internet community. It does not specify an Internet standard of any kind. Discussion and suggestions for improvement are requested.