It's an unusual day when the Australian Communications and Media Authority (ACMA) takes it upon itself to launch a set to help people check for a specific malware variant. So count today as unusual. The DNS-OK site was developed to help individuals check if their DNS settings have been maliciously altered by the DNSChanger malware, which spread rapidly in late 2011.
The site, developed in conjunction with CERT Australia, offers a pretty good explanation of the problem, as well as links to help affected individuals remove it. If you've followed good security practice, it shouldn't be a problem, but it's an easy way for less tech-savvy users to check.