| accept | The Accept request-header field can be used to specify certain media types which are acceptable for the response. Accept headers can be used to indicate that the request is specifically limited to a small set of desired types, as in the case of a request for an in-line image. |
| accept-charset | 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. |
| accept-encoding | The Accept-Encoding request-header field is similar to Accept, but restricts the content-codings that are acceptable in the response. |
| accept-language | The Accept-Language request-header field is similar to Accept, but restricts the set of natural languages that are preferred as a response to the request. |
| cache-control | The Cache-Control general-header field is used to specify directives that must be obeyed by all caching mechanisms along the request/response chain. The directives specify behavior intended to prevent caches from adversely interfering with the request or response. These directives typically override the default caching algorithms. |
| connection | The Connection general-header field allows the sender to specify options that are desired for that particular connection and must not be communicated by proxies over further connections. |
| header-order | The order of the header lines which are very characteristic for every implementation. |
| keep-alive | When the Keep-Alive connection-token has been transmitted with a request or a response, a Keep-Alive header field may also be included. |
| te | The TE request-header field indicates what extension transfer-codings it is willing to accept in the response and whether or not it is willing to accept trailer fields in a chunked transfer-coding. Its value may consist of the keyword "trailers" and/or a comma-separated list of extension transfer-coding names with optional accept parameters. |
| ua-color | The ua-color header is optional. The proprietary header field was introduced within Microsoft Internet Explorer 7.0 to transmit the color depth of the client device. |
| ua-pixels | The ua-pixels header is optional. The proprietary header field was introduced within Microsoft Internet Explorer 7.0 to transmit the display measurements of the client device. |
| ua-os | The ua-os header is optional. The proprietary header field was introduced within Microsoft Internet Explorer 7.0 to transmit the underlying operating system of the client device. |
| ua-cpu | The ua-cpu header is optional. The proprietary header field was introduced within Microsoft Internet Explorer 7.0 to transmit the underlying system architecture of the client computer. |
| user-agent | The User-Agent request-header field contains information about the user agent originating the request. This is for statistical purposes, the tracing of protocol violations, and automated recognition of user agents for the sake of tailoring responses to avoid particular user agent limitations. User agents should include this field with requests. |
