<P> Notice that no - cache is not instructing the browser or proxies about whether or not to cache the content . It just tells the browser and proxies to validate the cache content with the server before using it (this is done by using If - Modified - Since, If - Unmodified - Since, If - Match, If - None - Match attributes mentioned above). Sending a no - cache value thus instructs a browser or proxy to not use the cache contents merely based on "freshness criteria" of the cache content . Another common way to prevent old content from being shown to the user without validation is Cache - Control: max - age = 0 . This instructs the user agent that the content is stale and should be validated before use . </P> <P> The header field Cache - Control: no - store is intended to instruct a browser application to make a best effort not to write it to disk (i.e not to cache it). </P> <P> The request that a resource should not be cached is no guarantee that it will not be written to disk . In particular, the HTTP / 1.1 definition draws a distinction between history stores and caches . If the user navigates back to a previous page a browser may still show you a page that has been stored on disk in the history store . This is correct behavior according to the specification . Many user agents show different behavior in loading pages from the history store or cache depending on whether the protocol is HTTP or HTTPS . </P> <P> The Cache - Control: no - cache HTTP / 1.1 header field is also intended for use in requests made by the client . It is a means for the browser to tell the server and any intermediate caches that it wants a fresh version of the resource . The Pragma: no - cache header field, defined in the HTTP / 1.0 spec, has the same purpose . It, however, is only defined for the request header . Its meaning in a response header is not specified . The behavior of Pragma: no - cache in a response is implementation specific . While some user agents do pay attention to this field in responses, the HTTP / 1.1 RFC specifically warns against relying on this behavior . </P>

List the http headers that are sent by browser