In trying to register a user control, I get the following error:

Validation (XHTML 1.0 Transitional): Element 'register' is not supported

Seems simple enough. Any ideas?

I wrote in VB:
<%@ Register Src="Controls/UserProfile.ascx" TagName="UserProfile" TagPrefix="mb" %>
and placed it in the page:
<mb:UserProfile ID="UserProfile1" runat="server" />

Are you absolutely sure you typed it correctly? Did you put the % and @ in the Register tag, in the correct places?

If not, the validator would assume you are attempting to use an unsupported HTML tag, like this:

<Register ...

which is a no-no.

Yes i did use the % and the @. When I open the individual page the error still pops up. However, when I run the master page everything is OK. So maybe I'm good to go. Just weird. Thanks.

Is it possible you placed it in the body of the page somewhere, instead of at the very top of the page under the Page directive? It's weird that the XHTML validator would quibble about this if you typed it properly and put it in the right place. But then again, the VS2005 validator did have some weird quirks like that.

i have the exact same problem in a project i haven't changed in a long time and it worked fine last time i was in it now i have errors like that all over the place. did you get it resolved?