代码如下：

!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"
html xmlns="http://www.w3.org/1999/xhtml"
head
title/title
script src="js/Jquery1.7.js" type="text/javascript"/script
script type="text/javascript"
$(function () {
$('#Button1').click(function () {
var username = $('#txtUserName').val();
var pwd = $('#txtPwd').val();
$.ajax({
type: "post",
contentType: "application/json",
url: "WebService1.asmx/Login",
data: "{username:'" + username + "',pwd:'" + pwd + "'}",
success: function (bukeyi) {
if (bukeyi.d == 'true') {
window.location = 'HTMLPage1.htm';
}
else {
$('#divinfo').text("用户名或密码错误");
}
}
})
})
})
/script
/head
body
用户名input id="txtUserName" type="text" /br /
密码input id="txtPwd" type="text" /br /
input id="Button1" type="button" value="登录" /br /
div id="divinfo"/div
/body
/html

------WebService1.asmx----
代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
namespace ajax11
{
/// summary
/// WebService1 的摘要说明
/// /summary
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.ComponentModel.ToolboxItem(false)]
// 若要允许使用 ASP.NET AJAX 从脚本中调用此 Web 服务，请取消对下行的注释。
[System.Web.Script.Services.ScriptService]
public class WebService1 : System.Web.Services.WebService
{
[WebMethod]
public string HelloWorld()
{
return "Hello World";
}
[WebMethod]
public string ValidateUser(string username)
{
if (username == "onlifes")
{
return "用户名已被占用，请选择其他";
}
else
{
return "可以使用，请继续";
}
}
[WebMethod]
public string GetDate()
{
return DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss");
}
[WebMethod]
public string Login(string username, string pwd)
{
if (username == "admin" && pwd == "888888")
{
return "true";
}
else
{ return "false"; }
}
}
}