一款经典的ajax登录页面 后台asp.net(3)

    <script type ="text/javascript" >
        window.onload = function (){
            document.getElementById ('txtusername').focus();//用户名框获得焦点

            if (GetCookie('user_name') != null && GetCookie('user_pwd') != null)//设置记住密码的登录页面
            {
                document.getElementById ("txtusername").value = GetCookie('user_name');
                document.getElementById ("txtpwd").value = GetCookie('user_pwd');
            }
        }

        String.prototype.Trim = function() //自定义的去除字符串两边空格的方法
        { 
            return this.replace(/(^\s*)|(\s*$)/g, ""); 
        } 

        function checkuser()//检验用户名是否正确
        {
            var img = document.getElementById ("imgCheck")
            img.src="iamges/blue-loading.gif";//设置图片及其可见性
            img.style.visibility = "visible";

            var aj = new ajax();//以下为ajax请求
            var username = document.getElementById ("txtusername").value.Trim();
            var url = "login.aspx?uname="+escape(username);
            aj.get(url,callback);
            function callback(obj)
            {
                var response = obj.responsetext;
                var res = response.split('\n');
                if (res[0] == "ok")
                {
                    img.src="iamges/icon-info.gif";
                    document.getElementById ("unMessage").innerHTML = "<font color='#00ff00'>用户名正确</font>";
                }
                else
                {
                    img.src="iamges/icon-warning.gif";
                    document.getElementById ("unMessage").innerHTML = "<font color='#ff0000'>用户名错误</font>";
                }
            }
        }

        
        function login()//登录
        {
            if (document.getElementById ("unMessage").innerText == "用户名错误")
            {
                alert("你的用户名错误");
            }
            else if (document.getElementById ("txtpwd").value == "")
            {
                alert("请输入密码");
            }
            else
            {
                var aj = new ajax();
                var username = document.getElementById ("txtusername").value.Trim();
                var userpwd = document.getElementById ("txtpwd").value;
                var url = "login.aspx?name="+escape(username)+"&pwd="+escape(userpwd);
                aj.get(url,callback);
                function callback(obj)
                {
                    var response = obj.responsetext;
                    var res = response.split('\n');
                    if (res[0] == "ok")
                    {
                        if (document.getElementById ("cbRememberPwd").checked)
                        {
                            SetCookie('user_name',username,1);//保存密码一个月
                            SetCookie('user_pwd',userpwd,1);
                        }
                        else
                        {
                            SetCookie('user_name',username);
                            SetCookie('user_pwd',userpwd);
                        }
                        window.open ("loginIndex.htm","_self");
                    }
                    else
            &p;            {
                        alert("密码错误");
                    }
                }
            }
        }

        function reset()//重置
        {
            window.onload();//执行窗体登录事件
            document.getElementById ("txtusername").value="";
            document.getElementById ("txtpwd").value="";
        }

        function enterLogin()
        {
            if (event.keyCode==13) //如果按下的是Enter键的话，就执行登录语句
            {
                login();
            }
        }
    </script>

4，新建一名为login.aspx的页面，该页面作为ajax请求的页面，login.aspx.cs代码如下