Hypertext Transfer Protocol -- HTTP/1.1 - Header Field Definitions

http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html

http://www.php.net/manual/en/function.header.php

http://harry.iteye.com/blog/605749

http://www.laruence.com/2010/03/05/1332.html

http://www.cnblogs.com/yuyii/archive/2008/10/16/1312238.html

http://blog.wahahajk.com/2009/08/httpcache-control.html