求助 http header后面的编码

[simoreg]

我打算用VC写一个能够自动填写网页表格的程序
用Fiddler监控网页在浏览器中的行为
在按下网页上的确认按键后，捕捉其Header，每次Header的最下方有类似的东东

__VIEWSTATE=%2FwEPDwULLTEwMDI1MDQ5OThkZGAavolv9q90fvFrangrg1a6AE3T&R=A&NoFresh=1&TestTopic=jcB%2F1LJVm3OgXgp2tnVh1w%3D%3D&Grade=oNUFIsOCmeI%3D&Rnd=BcDeF
__VIEWSTATE=%2FwEPDwULLTEwMDI1MDQ5OThkZGAavolv9q90fvFrangrg1a6AE3T&R=C&NoFresh=1&TestTopic=ZVORXmxCbJg08Aurv3ZSIQ%3D%3D&Grade=oNUFIsOCmeI%3D&Rnd=fGhIj
__VIEWSTATE=%2FwEPDwULLTEwMDI1MDQ5OThkZGAavolv9q90fvFrangrg1a6AE3T&R=0&NoFresh=1&TestTopic=Mb5%2Fbd6DwUI0tath8bTXog%3D%3D&Grade=%2BQ4%2BNtGp%2F%2BU%3D&Rnd=KjHgF
__VIEWSTATE=%2FwEPDwULLTEwMDI1MDQ5OThkZGAavolv9q90fvFrangrg1a6AE3T&R=0&NoFresh=1&TestTopic=9Utc0CGVm5kmM24%2Fyuk2wA%3D%3D&Grade=87sYSbgRQuE%3D&Rnd=uTrQp

（以上三行分别代表我按下了三次按钮后，Header后面的东西）
请问，这是什么编码，代表什么意思？

[simoreg]

补充： Fiddle中捕捉的完整Header如下：（其中网址 Cookie 隐去，请大神见谅） POST http://XXXXXXXX/Web/Upgrade.aspx HTTP/1.1 Host: wgwsxx.cn Connection: keep-alive Content-Length: 150 Cache-Control: max-age=0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8 Origin: http://wgwsxx.cn User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.63 Safari/537.36 115Browser/5.2.7 Content-Type: application/x-www-form-urlencoded Referer: http://wgwsxx.cn/Web/Upgrade.aspx?tWorkType=5 Accept-Encoding: gzip,deflate,sdch Accept-Language: zh-CN,zh;q=0.8 Cookie: __VIEWSTATE=%2FwEPDwULLTEwMDI1MDQ5OThkZGAavolv9q90fvFrangrg1a6AE3T&R=0&NoFresh=1&TestTopic=ZZv184aOXfwee5QN1GTEew%3D%3D&Grade=oNUFIsOCmeI%3D&Rnd=yXwVu

[oyljerry]

cookie数据 带一些用户信息

[Dobzhansky]

asp.net 的视图状态，用于保存页面控件的状态信息