0.ac
Ambiguous Single Digit
Telephone Number Shorthand, Extension or Status Code

Telephone Extension 0
or
Status Code 0

0 by itself is ambiguous. ICUC thinks you might have entered an unknown telephone number shortcut abbreviation or a telephone number extension without a preceding telephone number or a status code without any telephone number to apply the status code to. To make use of telephone number shorthand abbreviations you must first perform a login from this device. After login, depending upon how you have set up your account, here are some valid ways to use a single .ac digit:

0.ac Ex: Access web site of recent telephone number who's last digit is 0
or
c.0.ac Ex: Calendar for last used telephone number ending in digit 0
or
e.0.ac Ex: Email last used telephone number ending in digit 0
or
i.0.ac Ex: Instant Message last used telephone number ending in digit 0
or
s.0.ac Ex: Get status of last used telephone number ending in digit 0
or
w.0.ac Ex: Access web site of recent telephone number who's last digit is 0
or
x.0.ac Ex: Access web site of recent telephone extension who's last digit is 0
or
800.555.1212.0.ac Ex: Access web site of telephone number 800.555.1212 extension 0
or
17.9797.800.555.1212.0.ac Ex: Set the status of telephone number 800.555.1212 x0 to status code 17 assuming that 9797 is a valid PIN code for performing status updates.

more information on telephone number shortcuts, extensions and status codes...