To use a custom CSS skin file you need to disable the built-in skin CSS files by setting EnableEmbeddedSkins property to false. If you set it to the RadDockLayout control, all inner RadDock and RadDockZone controls will inherit the setting. The same applies to the Skin property. The third step is to manually
register the CSS file for your custom skin in the page's HEAD tag.
The following example demonstrates the described technique:http://www.telerik.com/demos/aspnet/prometheus/Dock/Examples/PostIt/DefaultCS.aspx
Dimo will check your custom skin you sent in the support ticket and will send you guidelines how to modify it for "Prometheus".
All the best,
Valeri Hristov (Senior Developer, MCSD)