GetHub下载不成功时直接在IE浏览器访问下面网址：
https://github-windows.s3.amazonaws.com/GitHub.application
如果还是不成功
在ie浏览器设置-安全-信任站点添加 https://github-windows.s3.amazonaws.com/GitHub.application
然后下面打钩。在IE游览器访问 http://github-windows.s3.amazonaws.com/GitHub.application