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Unrecognized Tag Prefix or Device Filter ‘asp’

B01I0001 One of the companies I work for recently took over a project from another vendor.  As we started to maintain the site, we noticed that we could not drag and drop controls onto the page and get any more than a stub of  the control. <asp:hyperlink runat=”server”></hyperlink> is ALL we got when we dropped the hyperlink control onto the designer.

In fact, every ASPX control on the page displayed the error, “Unrecognized tag prefix or device filter ‘asp.’”

What’s up with that?

Thinking that there must be something wrong with our development environment, or at least something wrong with how we have the project configured, I started my search on Google.

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