问题描述：
原因分析：
服务器开启了https时，cookie的secure属性应设为true；
解决办法：
1.服务器配置https ssl方式，参考：https://support.microsoft.com/kb/324069/zh-cn
2.修改web.config，添加:
<system.web>
<httpcookies
httponlycookies="true" requiressl="true" />
<system.web>
see: http://msdn.microsoft.com/en-us/library/ms228262(v=vs.100).aspx
3.修改后台写cookies时的设置 cookie.secure = true：
httpresponse response = httpcontext.current.response;
var cookie = new httpcookie(key, value);
cookie.httponly = true;
cookie.path = "/";
cookie.expires = datetime.now.addhours(1);
cookie.secure = true;
response.appendcookie(cookie);
参考网站：http://stackoverflow.com/questions/5978667/how-to-secure-the-asp-net-sessionid-cookie