The country code top-level domain (also known as ccTLD) for Denmark is .dk.
The rights to use a .dk-domain can be acquired by anyone as long as the domain name hasn’t already been registered by another party. In this case, you can look up the current registrar of the domain name here (WHOIS).
A .dk-domain name can’t be bought, but it can be borrowed “indefinitely”. A yearly tax of approximately EUR 5 has to be paid.
The supervision of the .dk top-level domain is handled by the non-profit organisation DK Hostmaster. If you wish to register a new .dk-domain name you have to do it through one of the approved registrators – a complete list can be found here. You can find both Danish and foreign registrators.
Since 2005 it has been possible to register domain names with the characters æ, ø, å, ö, ä, ü, and é.