AutoCompleteExtender位置错误，不直接在文本框下

Question

我的AutoCompleteExtender工作正常，但扩展器处于错误的位置，远远落后于它 我试过这个链接here，但它没有用，这是在浏览器

                    <table border="0" cellpadding="0" cellspacing="0">
                    <tr>
                        <td>

                 <asp:DropDownList ID="DropDownList1" runat="server">
                    <asp:ListItem Value="Email">Email</asp:ListItem>
                    <asp:ListItem Value="UserName">User Name</asp:ListItem>
                </asp:DropDownList>
                       </td>
                        <td>
                 <asp:TextBox ID="TxtSearch" runat="server"></asp:TextBox>
                <ajaxToolkit:AutoCompleteExtender ID="AutoComplete1" runat="server" BehaviorID="AutoCompleteEx"
                    TargetControlID="TxtSearch" ServicePath="~/CMSWebServices/MemberService.asmx" ServiceMethod="SearchUsersByName"
                    MinimumPrefixLength="2" CompletionInterval="500" EnableCaching="true" CompletionSetCount="12" CompletionListElementID="TxtSearchPosition">
                </ajaxToolkit:AutoCompleteExtender>   
                <ul id="TxtSearchPosition"></ul>

                        </td>
                        <td>
                 <asp:Button ID="ButtonSearch" runat="server" Text="Search" />

                        </td>
                    </tr>
                </table>