手动创建ajax引擎

<script>
    function createXMLHttp(){
            var xmlHttp;
            if(window.ActiveXObject)
                xmlHttp=new ActiveXObject('Msxml2.XMLHTTP');
            else
                xmlHttp=new XMLHttpRequest();
            return xmlHttp;
    }
</script>
或者：
<script>
    function createXMlHttp(){
            try{return new ActiveXObject('Msxml2.XMLHTTP');}catch(e){}
            try{return new XMLHttpRequest();}catch(e){}
            alert('你的浏览器不支持ajax');
    }
    createXMlHttp();
</script>