Thank you for using our services.
The "Default2006" skin is
no longer used. It has been removed from Q1 RadControls for ASP.NET AJAX
distribution which we use. Instead Default2006 you can use "Default"
skin. Find the control with the ID="RadPanelBar1" and change the skin
property in the control declaration.
You can gather more information from the following discussion at http://www.telerik.com/community/
Let us know if there is anything else that we can do for you.
the Telerik team