The check is done by looking for a reverse pointer (PTR) and seeing if this is in the .dk domain. Furthermore it is checked that the .dk address has a valid ip-address. If your machine is in Denmark, and you have these problems, then you can contact your ISP and ask them to solve that problem.
We are sorry for the inconvenience. We advise you to use another site. For Linux-distributions, also foreign sites carry files that have the same support for Danish as the files on our machine.
You can contact webmaster AT klid.dk for further information.