Element 'elementname' is not supported.

I have VS2010. Web app project. Every aspx page has green lines under every asp control saying it is not supported.

For instance: Validation(): Element 'label' is not supported.

I get that error for the line:

<asp:label id="lblList" runat="server" cssclass="fieldValue"></asp:label>

The label is in a td in a tr in a table in a panel. The aspx pages do not have head, body sections because that is on the master page.

The app builds and runs fine. Just validation messages that annoy me, since I actually pay attention to those warnings and try to form good code. Immpossible now, when every single thing has a warning on it.