Your .ac domain name must:
* be at least 3 characters and no more than 63 characters long (except airline industry codes as described in "Industry Codes" ).
* not contain a hyphen on the 3rd and 4th position (tagged domains).
* contain only letters (a-z), numbers (0-9) and hyphens or a combination of these.
* start and end with an alphanumeric character, not a hyphen.
