I am working on the Trailhead "Use Static Resources" unit.  I see this in the instrutions - "Click Preview to open a preview of your page that you can look at while you make changes. A new window should open, showing the standard Salesforce page header and sidebar elements, and a short message from jQuery."  But I don't see the standard Salesforce page header and sidebare elements, I just see a bare browser window with just the little bit of jQuery ouput from the exercise.  I have noticed the same results in other training units.  Is there some setup that I am missing?  Thanks.