获取浏览器信息: F12

not good //有待改进

http://www.cnblogs.com/longze/archive/2013/06/07/3124354.html
http://www.itzhai.com/http-request-user-agent-determines-the-type-of-browser-requests-a-variety-of-ways-web-crawler-marked.html#read-more


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