Here's the link to one of the exercises where this is broken:
Basically, whenever you try to go to a view in the built-in browser, it returns a Not Found error. This happens any time I try and navigate to a specific route.
I think this Rails course requires urgent attention. It seems broken in pretty much every way possibly. I really think Codecademy should consider taking it down until they can fix it because trying to learn such a complex framework in a broken dev environment is a really bad idea for beginners.