http://httpd.apache.org/docs/2.2/en/mod/mod_cache.html http://httpd.apache.org/docs/2.2/ja/mod/mod_cache.html "Studying HTTP" HTTP Header Fields apacheの日本語のdocumentはversionが古くて、いくつかのdirectiveの説明が無い。他には Caching Guide のoverview "What Can be Cached?" の項目を読むと良い。 1. Caching must be enabled for this URL. See the CacheEnable and CacheDisable directives. 2. The response must have a HTTP status code of 200