Valid characters in a domain name may be letters (a-z), numbers (0-9), hyphens (-) and the characters added by IDN. Two hyphens in a row as the third and fourth characters of a domain name are not allowed. The name must not begin or end with a hyphen. Length: domain names below .co.at and .or.at: at least one character (e.g. t3.co.at and s.or.at), domain names below .AT: at least three characters. Maximum length: 63 characters.
