Invalid markup in XAML in Visual Studio 2013

If you get this error in designer when there’s clearly no error in your XAML:
- close all files open in Visual Studio
- close Visual Studio
- delete the .suo file near the .sln
- delete bin and obj folders

if still doesn't work you can try to delete all directories from:
%LocalAppData%\Microsoft\VisualStudio\12.0\Designer\ShadowCache

More info:
http://stackoverflow.com/questions/12871358/visual-studio-2012-xaml-designer-invalid-markup
http://forums.xamarin.com/discussion/10284/xamarin-new-pcls-w8-wp8-net45-xamarin-ios-xamarin-droid-plus-new-microsoft-bcl-terribly-broken