Websites change, go away and are taken down. But that doesn't stop courts and scholars of all types from citing, increasingly, to online sources in their work. The pervasive problem that results is called "link rot." See Jonathan Zittrain et al., Perma: Scoping and Addressing the Problem of Link and Reference Rot in Legal Citations, 127 Harv. L. Rev. F. 176 (2014), archived at http://perma.cc/4BLV-W28N.