缺少对象，老查不出原因，急～～！！！！


    function createXMLHttpRequest() {        if (window.XMLHttpRequest) { //Mozilla 浏览器
            xmlHttp = new XMLHttpRequest();
            if (xmlHttp.overrideMimeType) {//设置MiME类别
                xmlHttp.overrideMimeType("text/xml");
            }
        }
        else {
            if (window.ActiveXObject) { // IE浏览器
                try {
                    xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
                }
                catch (e) {
                    try {
                        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
                    }
                    catch (e) {
                    }
                }
            }
        }    }
    function Check_UserInfo()//检测用户信息
    {        var SalesCode = document.getElementById("SalesCode").value;
        if (SalesCode + "a" == "a") {
            document.getElementById("SalesCode").focus();
            return false;
        }
        var webFileUrl = "/ajax.aspx?Action=CheckUserInfo&SalesCode=" + escape(SalesCode);        createXMLHttpRequest();
        xmlHttp.onreadystatechange = function() {
            if (xmlHttp.readyState == 4) {
                if (xmlHttp.status == 200) {
                    var data = xmlHttp.responseText;
                    if (data + "a" != "a") {
                        var dataArray = data.split("|");
                        if (dataArray[0] + "a" != "a") {
                            document.getElementById("SalesName").value = dataArray[0];
                            document.getElementById("Phone").value = dataArray[1];
                            document.getElementById("Tell").value = dataArray[2];
                            document.getElementById("Age").value = dataArray[3];
                            document.getElementById("Address").value = dataArray[4];
                        }
                    }
                }
                else {
                    //document.getElementById(innerHTML).innerHTML="读取数据失败,请刷新页面.";   
                }
            }
            else {
                //document.getElementById(innerHTML).innerHTML="正在读取数据....";
            }
        }
        xmlHttp.open("POST", webFileUrl, true);
        xmlHttp.send("");
    }
提示 Check_UserInfo 缺少对象，那位大哥指点一下？　不胜感激