<table>
    <tr style="border-top:solid 1px black;">
    <td><asp:Label runat="server" ID="lb1" Text="TOPOLINO"></asp:Label></td>
     <td><asp:RadioButton runat="server" ID="rb1" GroupName="gruppo" AutoPostBack="true"></asp:RadioButton></td>
    </tr>
     <tr style="border-top:solid 1px black;">
     <td><asp:Label runat="server" ID="lb2" Text="PIPPO"></asp:Label></td>
     <td><asp:RadioButton runat="server" ID="rb2" GroupName="gruppo" AutoPostBack="true" ></asp:RadioButton></td>    
    </tr>
    </table>