后台：

    [WebMethod]
    public static string sayHi()
    {
        int i = 1;
        i += 1;
        return i.ToString();
    }

前台：

    $.ajax({
                    type: "post",
                    url: "ajaxHandler.aspx/sayHi",
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: function(data) {
                        $("#msg").css("color", "#0000FF").html(data.d);
                    },
                    error: function(err) {
                        $("#msg").css("color", "#FF0000").html("access faield:" + err);
                    }
                });

报错

1. {Message: "身份验证失败。", StackTrace: null, ExceptionType: "System.InvalidOperationException"}
1. ExceptionType:"System.InvalidOperationException"
2. Message:"身份验证失败。"
3. StackTrace:null