110 Response is Stale
HTTP Warning status code 110 Response is Stale is an unofficial HTTP status code, but instead is used in combination with the Warning HTTP Header and included with HTTP response messages to indicate that the HTTP response is stale. Specifically, this HTTP status code is generated by the cache when the time set for the HTTP response has expired.
The HTTP status code 110 Response is Stale and the Warning HTTP header have been deprecated.
Warning: 110 www.example.re "Response is Stale"