ajax提取JSP反应结果的HTML问题

<html>
 <head>
  <title> New Document </title>
 <script type="text/javastript">
 var xmlobj;

 function CreateXMLHttpRequest()
{
        if(window.ActiveXObject)
        {
            xmlobj = new ActiveXObject("Microsoft.XMLHTTP");
        }
        else if(window.XMLHttpRequest)
        {
            xmlobj = new XMLHttpRequest();
        }
}
function SubmitArticle()
{
    CreateXMLHttpRequest();
    var parm = "chaxun="+"selteachbuild="+document.getElementById("selteachbuild").value+ "thetime=" + document.getElementById("thetime").value;
    xmlobj.open("POST", "http://classroom.upc.edu.cn/kebiao_look.jsp", true);
    xmlobj.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;");
    xmlobj.onreadystatechange = StatHandler;
    xmlobj.send(parm);
}
function StatHandler()
{
        document.getElementById("showpage").innerHTML = xmlobj.responseText;
}
</script>
 </head>
 <body>
 <p><form action="">
  <input type="text" id="mold">
  <input name=thetime value="2013-05-30" style="width:80px;font-family:arial;font-size:15">
  <font face="隶书" size="4pt" >教学楼：</font>       
 <select name="selteachbuild" >

    <option value=东环>东环</option>

    <option value=西环>西环</option>

    <option value=南堂>南堂</option>

    <option value=东廊>东廊</option>

    <option value=西廊>西廊</option>

    <option value=多媒体>多媒体</option>

    <option value=南教楼>南教楼</option>

    <option value=文理楼>文理楼</option>

 </select>
 <input name="chaxun" type="button"  value="查询" onclick="SubmitArtcle();">
 </form></p>
 <p><div id="showpage"></div></p>
 </body>
 </html>

想通过AJAX达到不刷新页面获取HTML界面的目的。但是提交表单之后，总是得不到回复，怎么回事呢？

你的ajax怎么写的不贴上来怎么看啊

好像没有看到返回？response哪儿去了？