This is the web site where the magical girls get their powers. The site will open itself if a girl seems worthy of the power (e.g. leads a miserable life, bears a burning grudge, etc.). Once they have their powers, the only way to access it is with a drive in their magical wands.
The Tempest
"At 7:23 p.m. on August 11th, The Tempest will arrive. The Tempest will bring an end to this godforsaken world and open a doorway to a new world. But in the process, most of humanity will be lost. The Tempest's arrival may be inevitable, but there is one way you can survive. That is to satiate the king's hunger. The king feeds on humanity's negative energy, and offering it to him will allow you to avoid death during the Tempest. Negative energy can be collected and stored inside the magic sticks you received from the Magical Girl Site. Only the one who uses their stick to gather the most negative energy to offer will be unscathed by the coming Tempest. If you wish to survive, please deliver a magic stick fully charged with negative energy to the Magical Girl Site on the day of the Tempest. Until then, have a pleasant apocalypse."
If a Magical Girl clicks on a certain place on an admin, she could see a countdown. It is said numerous times - first by Yatsumura, later affirmed by the site itself - that this event means the destruction of mankind. The Admins state that only the magical girl who uses the most sticks and the most magic will survive the tempest due to the offering of negative energy. Although it is questionable how this would work, given that every use of a stick will lead to an irreversible loss of lifetime.