The Public response-header field lists the set of methods supported by the server. The purpose of this field is strictly to inform the recipient of the capabilities of the server regarding unusual methods. The methods listed may or may not be applicable to the Request-URI; the Allow header field (section 14.7) MAY be used to indicate methods allowed for a particular URI.
Public = "Public" ":" 1#method
Example of use:
Public: OPTIONS, MGET, MHEAD, GET, HEAD
This header field applies only to the server directly connected to the client (i.e., the nearest neighbor in a chain of connections). If the response passes through a proxy, the proxy MUST either remove the Public header field or replace it with one applicable to its own capabilities.