Lists the set of methods supported by the resource identified by the Request-URI. The purpose is to inform the recipient of valid methods associated with the resource.

Example:

Allow: GET, HEAD, PUT

Used as a modifier to the media-type, to indicate what additional data format transformations such as compression have been applied to the entity-body.

Example:

Content-Encoding: gzip

Specifies the natural language(s) of the intended audience for the enclosed entity.

Example:

Content-Language: en

Indicates the size (in octets) of the entity-body that is sent or that would have been sent if it has reen requested.

Example:

Content-Length: 3495

Supplies the resource location for the entity enclosed in the message when that entity is accessible from a location separate from the requested resource's URI.

Example:

Content-Location: http://www.httpheaders.com/index.htm

An MD5 digest of the entity-body for the purpose of providing an end-to-end message integrity check (MIC) of the entity-body.

Example:

Content-MD5: aASDA2sa3asDAS12dADAsS==

Sent with a partial entity-body to specify where in the full entity-body the partial body should be applied.

Example:

Content-Range: bytes 21010-47021/47022

Specifies the Internet media types of the entity-body that is sent or would have been sent if requested. Often includes a charset parameter specifying the character encoding.

Example:

Content-Type: text/html; charset=ISO-8859-4

Expires Gives the date/time after which the response is considered stale, for caching purposes. Example: Expires: Mon, 5 Aug 2002 19:43:31 GMT back to top

Note: The Expires header is important to cache control policies as it helps determine whether or not an entity is fresh. CacheRight, DynaCache, and XCache are some products that can help you with your cache control policies.

Last-Modified Indicates the date and time at which the origin server believes the variant was last modified. Example: Last-Modified: Mon, 5 Aug 2002 19:43:31 GMT back to top

Note: The Last-Modified header field is what is known as a validator. If a header does not contain any explicit freshness information about the entity, the user agent can use the Last-Modified header field to determine if an entity fresh. CacheRight, DynaCache, and XCache are some products that can help you with your cache control policies.