If you get this warning prompt, that means the WebGrid is unable to find the WebDesktop SmartWebResources Assembly in runtime. Ensure you have properly registered the SmartWebResources.
See Also
Tasks
FAQ: Does SmartWebResources feature automatically enabled in WebGrid.NET Enterprise 5.0?
FAQ: Briefly, what are the files included in WebGrid SmartWebResources Assembly?
FAQ: I am aware that WebGrid.NET Enterprise 5.0 requiring WebDesktop SmartWebResources as part of its User Interface engine. Do I need to purchase a separate WebDesktop's license in order to use its SmartWebResources?
How-to: Configure SmartWebResources in a new web application
How-to: Disable SmartWebResources for Localization's language files
Concepts
Hassle-free deployment through SmartWebResources™ technology