Patent granted Sep 2001 (filed 1998)
The idea that launched Google. A page is important if important pages link to it — authority flows through the link graph, computed recursively across the whole web.
⎘ US 6,285,999 B1 Method for node ranking in a linked database Assigns each node a score from the number and importance of nodes linking to it.Why it mattered for SEO. Made links the currency of ranking. Everything in the next two decades is a reaction to people gaming this one signal.
Mapping confidence: Foundational