I read about style here:
http://msdn.microsoft.com/en-us/library/cc278073(v=VS.95).aspx
I created a UserControl with slider and UserControl.Resources section. I paste the thumb style but some tag are not recognized like vsm:VisualStateManager (I'm using VS2010) why ?
That is the documentation for Silverlight. You probably want the documentation for WPF:
Edit:
Just to be clear, if you are using Silverlight, you should use Silverlight templates and styles; if you are using WPF, you should use WPF templates and styles.
In any case, the
VisualStateManager
is a full-fledged part of both Silverlight4 and WPF4, so if you see a template with the "vsm:" namespace, the simplest option is to just remove the prefix where-ever you see it.