Domain Names have a variety of basic rules, in general domains must: - Use only letters, numbers, or hyphen ("-"). - Cannot begin or end with a hyphen. - .com, .net, .org and .info domain names cannot exceed 67 characters total. - .info and .biz must have at least 3 characters not including .info or .biz. - Other domain names cannot exceed 22 characters, not including the extension. - Domain names are not case sensitive. - Domain names cannot include spaces. - 2 letter domains are not permitted. Strictly speaking domain shouldn't begin with a number either, however in practice it is possible in most circumstances.