$.ajax(
                    {
                        type: "GET",
                        url: "AddAdmin.aspx",
                        dataType: "html",
                        data: "userName=" + $("#TXT_USERNAME").val(),
                        beforeSend: function(XMLHttpRequest) {
                            $("#showResult").text("正在查询....");
                        },

                        success: function(msg) {

                            $("#div名").html(msg);

                            $("#div名").css("color", "red");

                            $("#div名").show("slow");
                            
                        },
                        complete: function(XMLHttpRequest, textStatus) {
                        //隐藏正在查询图片
                        },
                        error: function(XMLHttpRequest) {
                            aalert("出错了！"); //错误处理
                        }
                    }
                 );

string username = Request.QueryString["userName"];
            //string username=Request.Params["username"];

            if (INFO_ADMINManager.UserName(username))
            {
                Response.Write("用户名已存在！");
                Response.End();
            }
            else
            {
                Response.Write("您可以使用此用户！");