The Telerik.WebControls namespace was used in the RadControls for ASP.NET Classic suite that was discontinued over five years ago.
The current offering is called UI for ASP.NET AJAX and is based on MS AJAX, so it has a number of changes and improvements.
It is also important to note that we do not support .NET 2.0 since early 2011 (http://blogs.telerik.com/aspnet-ajax/posts/11-03-03/telerik-ajax-controls-net-2-0-support-discontinued-as-of-q1-2011.aspx
) and you are likely to need to upgrade your projects to a newer version.
Should you need to migrate your old projects, I can suggest examining migration articles like this one: http://www.telerik.com/help/aspnet-ajax/editor-migration-from-radeditor-classic-to-radeditor-prometheus.html
. Most controls that existed in the old suite have such articles in a similar place in the documentation.
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