In the tab container add this code now it will be fine working with tab control.. in this u can also add header template if needed to specify the name of tab panel..
<asp:TabPanel runat="server" ID="tpChangePassword" >
<ContentTemplate>
<asp:TextBox runat="server" Font-Bold="true" ID="txtCurrPwd" </asp:TextBox>
</ContentTemplate>
</asp:TabPanel>
HAPPY CODING:cool: