Hell Girl

Somewhere in the vast sea of the Internet, there's a website that can only be accessed at the stroke of midnight. Known as the Jigoku Tsushin, rumor has it that if you post a grudge there, the Jigoku Shoujo will appear and drag whoever torments you into the inferno. Very little is known about the girl—all we know for sure is that she lives with her equally enigmatic grandmother, that three magical straw dolls accompany and serve her, and that whenever a posting on the Jigoku Tsushin moves her, she becomes the Jigoku Shoujo.

Synopsis from Anime News Network