Link rot

Link rot (or linkrot), also known as link death, link breaking or reference rot, refers to the process by which hyperlinks on individual websites or the Internet in general point to web pages, servers or other resources that have become permanently unavailable. The phrase also describes the effects of failing to update out-of-date web pages that clutter search engine results. A link that does not work any more is called a broken link, dead link, or dangling link. Formally, this is a form of dangling reference: The target of the reference no longer exists.