百度：
2012.12.9 12:00
text/html
Sun, 09 Dec 2012 03:52:49 GMT
p_w_picpath/gif
Wed, 07 Dec 2022 03:52:49 GMT
application/javascript
Sun, 04 Dec 2022 08:50:17 GMT
涉及的http頭：
Expires
Content-Type
163.com
2012.12.9 12:00
text/html
Sun, 09 Dec 2012 03:56:32 GMT
p_w_picpath/png
Tue, 05 Feb 2013 20:03:36 GMT
p_w_picpath/jpeg
Thu, 07 Feb 2013 00:50:58 GMT