CacheNegotiatedDocs
CacheNegotiatedDocs Default: none Server config, virtual host
If present in the Config file, this directive allows content-negotiated documents to be cached by proxy servers. This could mean that clients behind those proxys could retrieve versions of the documents that are not the best match for their abilities, but it will make caching more efficient.
This directive only applies to requests that come from HTTP 1.0 browsers. HTTP 1.1 provides much better control over the caching of negotiated documents, and this directive has no effect on responses to HTTP 1.1 requests. Note that very few browsers are HTTP 1.0 anymore.