asp.net的gridview中列边框线总在哪设置呀？

<HeaderTemplate>
                                <table  width="779" borderstyle="solid">
                                <tr borderstyle="solid">
                                <td width="10%" borderstyle="solid">状态</td>
                                <td width="40%">主题</td>
                                <td width="15%" align="center">作者</td>
                                <td width="20%" align="center">回复/人气</td>   
                                <td width="15%" align="center">更新时间</td> 
                                </tr></table>
                               </HeaderTemplate>
                               <ItemTemplate>
                                <table  width="779" borderstyle="solid">
                                 <tr borderwidth="1" borderstyle="solid">
                                  <td width="10%" align="center" borderstyle="solid"><asp:Image runat="server" id="imag1" ImageUrl="../images/space.gif" /></td>
                                  <td width="40%" align="center" borderwidth="1"  borderstyle="solid"><%#DataBinder.Eval(Container.DataItem,"title")%></td>
                                  <td width="15%" align="center" borderwidth="1" borderstyle="solid"><%#DataBinder.Eval(Container.DataItem,"authorname")%></td>
                                  <td width="20%" align="center" borderwidth="1" borderstyle="solid"><%#DataBinder.Eval(Container.DataItem,"reviewnumber")%></td>  
                                  <td width="15%" align="center" borderwidth="1" borderstyle="solid"><%#DataBinder.Eval(Container.DataItem,"addtime")%></td>  
                                 </tr>
                                </table> 
                                </ItemTemplate>         
                 <ItemStyle BorderColor="Black" />还是没有任何的列框线显示呀？