A domain name can only contain the letters A-Z, the digits 0-9 and hyphen (-), in addition to one punctuation (.) used for grouping the domains in hierarchies, e.g.
under .no or .com. Some top level domains allow international characters such as Æ, Ø and Å, though these are encoded in a special way making the encoded domain name containing A-Z, 0-9 and hyphens.
A domain name must contain between 2 and 63 characters before the punctuation.
Additional rules apply for the different top level domains. In order to find out if a certain domain name is legal, try and search at domainnameshop.com. An error message will be displayed if it cannot be registered.
A domain name is not case sensitive, making Domainnameshop.Com the same as domainnameshop.com. However, most people use lowercase letters. Also note that the prefix "www." is not usually a part of the
domain name applied for. For a website named www.example.com, the domain name is solely example.com. www.example.com is only one of many possible sub domains under example.com.