The basic premise of this test is that the Conficker worm when it is infecting your computer blocks access to certain antivirus sites. What this page does is loads two known URLs that the worm will block (Norton and McAfee) into IFRAME (inline frame) elements on this page. If the websites in these frames don't load then there is a good chance you have a Conficker infection or something similar. Keep in mind the fact that these pages do load doesn't mean that you don't have some sort of other infection including a newer version of Conficker that acts differently. It's just a quick sanity check.