AJAX AutoCompleteExtender

各位：
   我用ajax AutoCompleteExtender做出查询的效果，但是结果没有显示像下拉列表框那样的效果，请问如何调样式？
前台代码：
                <asp:TextBox ID="txtBM" runat="server">
                </asp:TextBox>
                <div id="autoComplete">
                </div>
                <cc1:AutoCompleteExtender ID="ACE1" runat="server" MinimumPrefixLength="1" TargetControlID="txtBM"
                    CompletionInterval="1" EnableCaching="false" CompletionListElementID="autoComplete"
                    ServicePath="~/webService/WebService1.asmx" ServiceMethod="GetMyString" CompletionListCssClass="autocomplete_completionListElement">
                </cc1:AutoCompleteExtender>样式：
       .autocomplete_completionListElement
        {
            margin: 0px !important;
            background-color: inherit;
            color: windowtext;
            border: buttonshadow;
            border-width: 1px;
            border-style: solid;
            cursor: 'default';
            overflow: auto;
            height: auto;
            max-height: 200px;
            text-align: left;
            list-style-type: none;
        }