If you ever wondered if there are black holes in the Internet - you're right. Ethan Katz-Bassett, a computer science Ph.D. candidate from the University of Washington used his tool Hubble to detect that 10% of all sites on the Internet are unreachable, day by day. Problems reach from total unavailability up to various routing problems. 75% of these problems get fixed within an hour, some last for several days. If only the right sites would die everyday... (Source)