RadTabStrip allows you to define hierarchical tabs.
You can create a hierarchy by defining the structure with
the design-time builder, binding the control to a
hierarchical datasource or building its structure using the server-side
API.
This example shows a hierarchy defined inline in the aspx page:
<telerik:RadTabStrip id="RadTabStrip1" runat="server">
<Tabs>
<telerik:RadTab Text="Corporate">
<Tabs>
...
</Tabs>
</telerik:RadTab>
</telerik:RadTabStrip>