ajax 的使用错误？怎么处理？？？？

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>无标题页</title>    <script>
// 1. 初始化 请求 对象
// Mozilla/Firefox 下的
//var xmlhttp = new XMLHttpRequest();
// IE 下的
var xmlhttp=new ActiveXObject("Microsoft.XMLHTTP")
//alert(xmlhttp);function ajaxTest(data) {
    // 指定要打开的页面
    //alert(data.title);
   
    var url="Default2.aspx?sbid="+data.title;
    xmlhttp.open("GET", url, true);// HTTP 请求的方式, URL, 是否异步
    // 指定页面打开完之后要进行的操作.
    xmlhttp.onreadystatechange = mychange;
    // 开始发起浏览请求, Mozilla 必须加 null
    xmlhttp.send(null);
}// 这个函数就是每次状态改变要调用的函数
function mychange() {
    // 请求已完成
    if(xmlhttp.readyState == 4) {
        //alert(xmlhttp.readyState);
        alert(xmlhttp.responseText);
        // 更新对应的 HTML 元素里面显示的内容
    // 根据 ID 引用页面里面的元素 document.getElementById(元素名)
    document.getElementById('div1').innerHTML = xmlhttp.responseText;
    }
}
    </script></head>
<body>
    <form id="form1" runat="server">
        <div>
            <div>
                <asp:DataList ID="DataList1" runat="server" DataKeyField="Bid" DataSourceID="SqlDataSource1"
                    RepeatDirection="Horizontal">
                    <ItemTemplate>
                        <div runat="server" onmouseover="ajaxTest(this)" style="display: inline; border: solid 2px black;
                            margin-left: 7px" title='<%# Eval("Bid") %>'>
                            |
                            <asp:Label ID="BContentLabel" runat="server" Text='<%# Eval("BContent") %>'></asp:Label><br />
                        </div>
                        <br />
                    </ItemTemplate>
                </asp:DataList><asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:pubsConnectionString %>"
                    SelectCommand="SELECT * FROM [BigTitle]"></asp:SqlDataSource>
            </div>
            
            <div id="div1"></div>
            <asp:DataList ID="DataList2" runat="server" DataKeyField="Sid" DataSourceID="SqlDataSource2">
                <ItemTemplate>
                    <asp:Label ID="SContentLabel" runat="server" Text='<%# Eval("SContent") %>'></asp:Label><br />
                    <br />
                </ItemTemplate>
            </asp:DataList><asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:pubsConnectionString2 %>"
                SelectCommand="SELECT * FROM [SmallTitle] WHERE ([S_Bid] = @S_Bid)">
                <SelectParameters>
                    <asp:QueryStringParameter DefaultValue="1" Name="S_Bid" QueryStringField="sbid" Type="Int32" />
                </SelectParameters>
            </asp:SqlDataSource>            
        </div>
    </form>
</body>
</html>