Keypad Navigation

In general, 6 means forward, 4 means back, 5 means drill down into detail, and 2 means up. If you look at your cell phone keypad, you'll see that this key assignment is pretty intuitive. Stare at your phone long enough, and you'll see an iPod, but with a lot more potential for the user interface.

And for you power users, 9 means go forward a week, and 1 means go back a week.