HTTP wird vom World Wide Web Consortium (W3C) spezifiziert. Dort findet man auch die Spezifikation zu HTTP 1.0 (RFC 1945 [ca.137k groß]) und HTTP 1.1 (RFC 2068 [ca.378k groß]). Beide Dateien liegen im Textformat vor. Eine HTML-Version von HTTP 1.0 gibts bei der IETF HTTP. Für den geneigten Leser gibts auf beiden Servern auch die RFC 2109, die sich mit den Keksen (Cookies) auseinandersetzt. Nur heißt es dort sehr lapidar: "HTTP State Management Mechanism". (RFC 2109 beim W3C & bei der IETF). Weitere interessante Links zum Thema gibts findet man beim W3C wie auch bei der IETF-HTTP.
HTTP-Server, Proxy-Caches und Browser tauschen beim HTTP verschiedene Return-Codes aus. Diese Codes und ihre Bedeutung sind in der nachfolgenden Tabelle zusammengefaßt.
| Code | Bedeutung | HTTP-Version |
|---|---|---|
| Successful 2xx | ||
| 200 | OK | HTTP 1.0 |
| 201 | Created | HTTP 1.0 |
| 202 | Accepted | HTTP 1.0 |
| 203 | Non-Authoritative Information | HTTP 1.1 |
| 204 | No Content | HTTP 1.0 |
| 205 | Reset Content | HTTP 1.1 |
| 206 | Partial Content | HTTP 1.1 |
| Redirection 3xx | ||
| 300 | Multiple Choices | HTTP 1.0 |
| 301 | Moved Permanently | HTTP 1.0 |
| 302 | Moved Temporarily | HTTP 1.0 |
| 303 | See Other | HTTP 1.1 |
| 304 | Not Modified | HTTP 1.0 |
| 305 | Use Proxy (proxy redirect) | HTTP 1.1 |
| Client Error 4xx | ||
| 400 | Bad Request | HTTP 1.0 |
| 401 | Unauthorized | HTTP 1.0 |
| 402 | Payment Required | HTTP 1.1 |
| 403 | Forbidden | HTTP 1.0 |
| 404 | Not Found | HTTP 1.0 |
| 405 | Method Not Allowed | HTTP 1.1 |
| 406 | Not Acceptable | HTTP 1.1 |
| 407 | Proxy Authentification Required | HTTP 1.1 |
| 408 | Request Timeout | HTTP 1.1 |
| 409 | Confict | HTTP 1.1 |
| 410 | Gone | HTTP 1.1 |
| 411 | Length Required | HTTP 1.1 |
| 412 | Precondition Failed | HTTP 1.1 |
| 413 | Request Entity To Large | HTTP 1.1 |
| 414 | Request-URI To Long | HTTP 1.1 |
| 415 | Unsupported Media Type | HTTP 1.0 |
| Server Error 5xx | ||
| 500 | Internal Server Error | HTTP 1.0 |
| 501 | Not Implemented | HTTP 1.0 |
| 502 | Bad Gateway | HTTP 1.0 |
| 503 | Service Unavailable | HTTP 1.0 |
| 504 | Gateway Timeout | HTTP 1.1 |
| 505 | HTTP Version Not Supported | HTTP 1.1 |
Nachfolgend die Return-Codes, die Einfluß auf das Caching haben.
| Code | Bedeutung für's Caching | HTTP-Version |
|---|---|---|
| Successful 2xx | ||
| 200 | Cache unless a query response without expire information | HTTP 1.0 |
| 203 | Cache unless a query response without expire information | HTTP 1.1 |
| 204 | Negatively cached if no expire headers | HTTP 1.0 |
| Redirection 3xx | ||
| 300 | Cached | HTTP 1.0 |
| 301 | Cached | HTTP 1.0 |
| 302 | Cached only if expire information | HTTP 1.0 |
| 303 | Not cached | HTTP 1.1 |
| 304 | Not cached | HTTP 1.0 |
| 305 | Negatively cached if no expire headers | HTTP 1.1 |
| Client Error 4xx | ||
| 400 | Negatively cached if no expire headers | HTTP 1.0 |
| 401 | Not cached | HTTP 1.0 |
| 403 | Negatively cached if no expire headers | HTTP 1.0 |
| 404 | Negatively cached if no expire headers | HTTP 1.0 |
| 405 | Negatively cached if no expire headers | HTTP 1.1 |
| 407 | Not cached | HTTP 1.1 |
| 410 | Cached | HTTP 1.1 |
| 414 | Negatively cached if no expire headers | HTTP 1.1 |
| Server Error 5xx | ||
| 500 | Negatively cached if no expire headers | HTTP 1.0 |
| 501 | Negatively cached if no expire headers | HTTP 1.0 |
| 502 | Negatively cached if no expire headers | HTTP 1.0 |
| 503 | Negatively cached if no expire headers | HTTP 1.0 |
| 504 | Negatively cached if no expire headers | HTTP 1.1 |
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