is the HTTP web resource handler some of RadControls use to fetch scripts, styles and sprite images. Unfortunately, ASP.NET resource handlers are not very much venerated by web security products, as they are often treated as a web security vulnerability. Part of the suspicious behavior of the script resource handlers is that there is no physical file named WebResource.axd (or ScriptResource.axd for standard ASP.NET ScriptManager) present in the web site root.
Try creating an empty WebResource.axd file and see if you are getting the same warnings.
the Telerik team