This section defines the syntax and semantics of all standard HTTP/1.1 header fields.
For entity-header fields, both sender and recipient refer to either the client or the server, depending on who sends and who receives the entity.
The Accept request-header field can be used to specify certain media types which are acceptable for the response.
media-range = ( "*/*" | ( type "/" "*" ) | ( type "/" subtype ) ) *( ";" parameter ) accept-params = ";" "q" "=" qvalue *( accept-extension ) accept-extension = ";" token [ "=" ( token | quoted-string ) ] The asterisk "*" character is used to group media types into ranges, with "*/*" indicating all media types and "type/*" indicating all subtypes of that type.The media-range MAY include media type parameters that are applicable to that range.Each media-range MAY be followed by one or more accept-params, beginning with the "q" parameter for indicating a relative quality factor.The first "q" parameter (if any) separates the media-range parameter(s) from the accept-params.However, unless the user agent is a closed system which cannot interact with other rendering agents, this default set ought to be configurable by the user.
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. Each charset MAY be given an associated quality value which represents the user's preference for that charset. An example is The special value "*", if present in the Accept-Charset field, matches every character set (including ISO-8859-1) which is not mentioned elsewhere in the Accept-Charset field.If no "*" is present in an Accept-Charset field, then all character sets not explicitly mentioned get a quality value of 0, except for ISO-8859-1, which gets a quality value of 1 if not explicitly mentioned.Quality factors allow the user or user agent to indicate the relative degree of preference for that media-range, using the qvalue scale from 0 to 1 (section 3.9). Note: Use of the "q" parameter name to separate media type parameters from Accept extension parameters is due to historical practice.Although this prevents any media type parameter named "q" from being used with a media range, such an event is believed to be unlikely given the lack of any "q" parameters in the IANA media type registry and the rare usage of any media type parameters in Accept.Future media types are discouraged from registering any parameter named "q".