It is not completely clear what you are supposed to be looking at on the link as it contains lots of different items. You need to click on the Living in Greece link about halfway down the page and then the Registering with Greek Authorities link. That takes you to a link to a pdf document on registration requirements. Alternatively you can go directly to the pdf document here
. The information is broadly in line with information earlier on this thread. It contains images of the front page of the registration certificate, as posted by Filippos, and the permanent residence certificate so people should be able to recognise what they have got. If anybody still has the old residence permit then it has certainly expired.