各位高手帮帮忙，这是什么问题，复制的代码，出现找不到资源

 var xmlHttp;
     function createXMLHttpRequest() {
         if (window.ActiveXObject) {
             xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
         }
         else if (window.XMLHttpRequest) {
             xmlHttp = new XMLHttpRequest();
         }
     }

     function AjaxCheckUserID() {
         var txtName = document.getElementById("UserID");
         var txtRound = document.getElementById("CheckUserIDMeg");
         if (txtName.value == "") {
             txtRound.innerHTML = "请先输入用户名！";
             return;
         }
         createXMLHttpRequest();
         var getUserID = document.getElementById("UserID").value;
         var url = "CheckNameHandler.ashx?UserID=" + getUserID;
         xmlHttp.open("POST", url, false);
         xmlHttp.onreadystatechange = resultCheckName;
         xmlHttp.send(null);
     }

     function resultCheckName() {
         var txtRound = document.getElementById("CheckUserIDMeg");
//         if (xmlHttp.readystate == 4) {
//             if (xmlHttp.status == 200) {
                 var txtGetResponse = xmlHttp.responseText;
                 txtRound.innerHTML = txtGetResponse;
                 //return;
                 if (txtGetResponse) {
                     //txtRound.style.color = "#FF0000";
                     //txtRound.innerHTML = "已被注册，请使用新的用户名！";
                 }
                 else {
                     txtRound.style.color = "black";
                     txtRound.innerHTML = "该用户名可用！";
                 }
//             }
//         }
    }