<script language="javascript">
var http_request=false;
function send_request(url){//初始化,指定处理函数，发送请求的函数
http_request=false;
//开始初始化XMLHttpRequest对象
if(window.XMLHttpRequest){//Mozilla浏览器
http_request=new XMLHttpRequest();
if(http_request.overrideMimeType){//设置MIME类型
http_request.overrideMimeType("text/html");
}
}
else if(window.ActiveXObject){//IE浏览器
try{
http_request=new ActiveXObject("Xsxml2.XMLHTTP");
}
catch(e){
try{
http_request=new ActiveXObject("Microsoft.XMLHTTP");
}
catch(e){
}
}
}
if(!http_request){//异常，创建对象实例失败
window.alert("不能创建XMLHttpRequest对象实例");
return false;
}
http_request.onreadystatechange=processRequest;
//确定发送请求的方式和URL以及是否同步执行下段代码
http_request.open("GET",url,true);
http_request.send(null);
}
//处理返回信息的函数
function processRequest(){
if(http_request.readyState==4){//判断对象状态
if(http_request.status==200){//信息已经成功返回，开始处理信息
alert(http_request.responseText);
}
else{//页面不正常
alert("您所请求的页面有异常");
}
}
}
function userCheck(){
var f=document.form1;
var username=f.username.value;
if(username==""){
window.alert("用户名不能为空");
f.username.focus();
return false;
}
else{
send_request('jiaoyan.asp?username='+username);
}
}
</script>

<form id="form1" name="form1" method="post" action="">
  <table width="200" border="1">
    <tr>
      <td>&nbsp;</td>
      <td>数据校验演示</td>
    </tr>
    <tr>
      <td>用户名:</td>
      <td><label>
        <input name="username" type="text" id="username" size="15" />
      </label></td>
    </tr>
    <tr>
      <td>&nbsp;</td>
      <td><label>
        <input type="button" name="Submit" value="校  验" onclick="userCheck();"/>
      </label></td>
    </tr>
  </table>
</form>

jiaoyan.asp

<%
username=request("username")
if username="qianqian" then
Response.Write("Loveing?")
else
Response.Write("Loveing2?")
end if
%>