Hi, I'm reporting an issue that appeared for the first time in VS2012 and that is still present in VS2013. VS2010 doesn't have this problem. We created several user and server controls that we use inside our web pages. Starting from VS2012 every time I open the markup view a see an "Element 'myCustomControl' is not a known element. This can occur if there is a compilation error in the Web site, or the web.config file is missing." for every control.
Register headers are ok, if I switch to design view I see the error box that complains about a missing library but that library is referenced in the project and if I use the refresh button everything goes ok in design but in markup view the errors remain. At runtime everything work fine.
Probably there's something in my project structure that VS2012/2013 doesn't accept but how can I find the problem? I can't find any more descriptive message that explain me how to fix my code.