Are you are a licensed developer but you still sometimes get the trial message when you run a page with RadControls for ASP.NET AJAX?
Telerik.Web.UI 2012.X.XXX.XX trial version. Copyright Telerik © 2002-2012. To remove this message, please purchase a developer version.
This error means that you are still using the trial version of Telerik.Web.UI.dll! There is a couple of different ways to check whether the Telerik.Web.UI.dll assembly is a trial or a purchased one:
If you download your files from your Telerik.com account, make sure that they are DEV (the purchased) builds, to ensure that you not see a trial message, e.g.
If you have installed a trial build (.msi), it is recommended to uninstall it completely, download the Dev executable from your account and install it. More information on the subject is available in the following help article: Upgrading RadControls Trial to RadControls Developer license or newer version.
Stoyan Stratev is a technical lead in the Windows 8 HTML team at Telerik. He joined the company in 2005 as a web developer, specializing in the integration of the Telerik components in third-party solutions, such as DotNetNuke and SharePoint. He led one of the ASP.NET AJAX teams before moving on to the Windows 8 division.