Expires
| Expires |
The Expires header gives a date and time at which the response is no longer valid. This allows clients such as your browser to cache a copy and not have to ask the server if it is still valid until after this time has expired.
Chapter 7 discusses how the Expires header is used-in particular, how it relates to caches and having to revalidate responses with the origin server.
Type
Entity header
Basic Syntax
Expires: HTTP-date
Example
Expires: Thu, 03 Oct 1997 17:15:00 GMT