出错提示：Sys.WebForms.PageRequestManagerParserErrorException:The message received from the server
count not be parsed.Common causes for this error are when the response is modified by calls to response.Write(),response filters,HttpModules,or server trace is enabled.

在使用updatepanel时不能直接在后台使用Response.Write输出或用JS弹出窗口，应该改用ScriptManager.RegisterStartupScript(this.UpdatePanel1, this.GetType(), "updateScript", "alert('对不起，账号和密码错误');", true); 这样的方式来输出。