The quickest way to show (or hide) offline contacts is to press ctrl + H on your keyboard!

Here's how to show (or hide) your Address Book contacts, or show (or hide) empty groups:

1. Look just above the list of names in your Contact List for the message "type some contact information…."
2. On the right end of that bar is a down-arrow. Click the down-arrow to open a menu of viewing options.
3. Now just click on a selection to show (or hide) your Address Book contacts, or show (or hide) empty groups in your Contact List.