AirPort: How to reset the trusted networks list

Your computer keeps its list of trusted AirPort networks in the AirPort preferences file, "com.apple.airport.preferences.plist". It's located here:

/Library/Preferences/SystemConfiguration/

Deleting this file will reset the list. As a result, you will see a confirmation dialog whenever you attempt to join a network that was formerly in your trusted list. You might reset the list, for example, if your computer was automatically joining a network that you'd prefer to manually authorize. To delete the preference file in AirPort 3.3 or later, do the following steps.

For Mac OS X 10.3 "Panther"

1. While connected to a wireless network, locate the preference file "com.apple.airport.preferences.plist".
2. Drag it to the Trash.
3. In the resulting Authenticate dialog, enter your administrator name and password.
4. Click the AirPort menu bar icon, and choose Turn AirPort Off.
5. From the same menu, turn AirPort back on.

Once AirPort is on, the system creates a new preference file. Make sure that you don't skip any steps or the list may not be reset.

For Mac OS X 10.4 "Tiger"

1. From the Apple menu, choose Location > Network Preferences.
2. From the Show pop-up menu, choose AirPort.
3. Locate the pop-up menu next to "By default, join:". If this pop-up menu is set to "A specific network," this means that you upgraded to Tiger from Panther, and you should stop here and follow the Panther steps, above, instead. Otherwise, continue to step 4.
4. Set the pop-up menu to Preferred, which will reveal the list of trusted networks.
5. Select any network you want to delete from the list, then click the minus (-) button to delete it.
6. Click the Apply Now button.