<script type="text/javascript" language="javascript">
// src http://woooh.com/post/learn_ajax.html

var http_request = false;

function sendRequest(url, obj) {
    http_request = false;

    if (window.XMLHttpRequest) { // Mozilla, Safari,...

        http_request = new XMLHttpRequest();
        if (http_request.overrideMimeType) {
            http_request.overrideMimeType('text/xml');
        }
    } else if (window.ActiveXObject) { // IE

        try {
            http_request = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
            try {
                http_request = new ActiveXObject("Microsoft.XMLHTTP");
            } catch (e) {}
        }
    }

    if (!http_request) {
        alert('Giving up :( Cannot create an XMLHTTP instance');
        return false;
    }
    
    http_request.onreadystatechange = function processRequest() {
        //最后输出过程

        if (http_request.readyState == 4) {
            if (http_request.status == 200) {
                document.getElementById(obj).innerHTML=http_request.responseText;
                //alert(http_request.responseText);

            } else {
                alert('There was a problem with the request.');
            }
        }
    }
    
    document.getElementById(obj).innerHTML="waiting...";
    http_request.open('GET', url, true);
    http_request.send(null);
}
</script>