The browser is automatically putting "www." in front of "dk" allowing it to resolve. Although the root DNS zone (the implied dot at the end of DNS names) can have A records in it, the current policy only allows A records for (some) nameservers. As a result, the new gTLD program, for example, does not currently allow "bareword domains" because you can't put an A record for the domain by itself in the root zone. (The policy doesn't allow an MX record, either, so email to someone@shop wouldn't be possible without a policy change.) The policy is aimed at keeping the root zone simple, and minimizing the volume of changes.