http 304

http://stackoverflow.com/questions/1665082/http-status-code-200-cache-vs-status-code-304

http://niutuku.com/tech/www/304-Not-Modified.shtml

http://www.usity.org/1524.html

http://www.nginx.cn/939.html

 

http://blog.csdn.net/my_yang/article/details/7819225

 

http://www.blogjava.net/zjusuyong/articles/304788.html