Element is not a known element warning in Visual Studio when using User controls

Question

I have a Visual Studio 2008 project that is showing the following warning when using User Controls, and I haven’t been able to find a solution anywhere.

Answer 1

From the OP:

The apparent solution to this is to make sure that the TagName is the name of control class.

So for my example, the following displayed the warning:

<%@ Register Src="~/path/to/Control.ascx" TagName="tagName" TagPrefix="tagprefix" %>

But changing it to:

<%@ Register Src="~/path/to/Control.ascx" TagName="Control" TagPrefix="tagprefix" %>

fixes it.