The Accept-Charset request-header field can be used to indicate what character sets are acceptable for the response. This field allows clients capable of understanding more comprehensive or special- purpose character sets to signal that capability to a server which is capable of representing documents in those character sets. The ISO- 8859-1 character set can be assumed to be acceptable to all user agents.
Accept-Charset = "Accept-Charset" ":" 1#( charset [ ";" "q" "=" qvalue ] )
Character set values are described in section 3.4. Each charset may be given an associated quality value which represents the user's preference for that charset. The default value is q=1. An example is
Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
If no Accept-Charset header is present, the default is that any character set is acceptable. If an Accept-Charset header is present, and if the server cannot send a response which is acceptable according to the Accept-Charset header, then the server SHOULD send an error response with the 406 (not acceptable) status code, though the sending of an unacceptable response is also allowed.