Formatting Domain Names--域名可以由哪些字符串组成

the domain name can include any of the following printable ASCII characters (excluding spaces):

a-z
0-9
- (hyphen)
! " # $ % & ' ( ) * + , - / : ; < = > ? @ [  ] ^ _ ` { | } ~ .

http://docs.aws.amazon.com/Route53/latest/DeveloperGuide/DomainNameFormat.html