This is yet another sign that OS X Mavericks will launch soon: Apple just send a notification (shown above) to all users running the new OS X Mavericks Developer Preview 7 that will probably also greet anyone who will update their system to Mavericks.
The notification says “Take a tour now, or view it later from the Finder Help menu.”
Basically, it’s just a link to this new Apple website. The website itself is pretty barebones for now, but when Mavericks launches, it’ll supposedly be a tour around the new features present in Apple’s newest installment of the OS X series.