//<![CDATA[
//创建XMLHttpRequest
function createXMLHttpRequest() {
    var xmlHttp;
    if (window.XMLHttpRequest) {
        xmlHttp = new XMLHttpRequest();
    } else {
        var a = ["MSXML2.XMLHTTP.5.0", "MSXML2.XMLHTTP.4.0", "MSXML2.XMLHTTP.3.0", "MSXML2.XMLHTTP", "MICROSOFT.XMLHTTP.1.0", "MICROSOFT.XMLHTTP.1", "MICROSOFT.XMLHTTP"];
        for (var i = 0; i < a.length; i++) {
            try {
                xmlHttp = new ActiveXObject(a[i]);
                break;
            }
            catch (e) {
            }
        }
    }
    return xmlHttp;
}

//发GET请求
function sendGet(req, url, f) {
    req.open("GET", url, true);
    req.onreadystatechange = f;
    req.send(null);
}
//发POST请求
function sendPost(req, url, f, param) {
    req.open("POST", url, true);
    req.setRequestHeader("If-Modified-Since", "0");
    req.setRequestHeader("Cache-Control", "no-cache,no-store");
    req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
    req.onreadystatechange = f;
    req.send(param);
}
//]]>