某些变态的WEB服务器不认全小写的请求头, 特别是Cookie这个字段.

Header Field Definitions ... 14

http://www.w3.org/Protocols/rfc2616/rfc2616.html
http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14


http://www.w3.org/Protocols/rfc2616/rfc2616-sec5.html#sec5.3

Example:

![image](https://f.cloud.github.com/assets/1265888/1224429/8b74f6bc-274a-11e3-9c85-6ae090fcd6be.png)

![image](https://f.cloud.github.com/assets/1265888/1224431/939219c4-274a-11e3-93d5-ee73fe6348dd.png)