Google has used links to determine the authority of websites since its early days: the idea of webpages casting votes for other pages by linking to them is at the core of the PageRank algorithm. This led to the rise of numerous manipulative link tactics. Google reacted with the Penguin update and manual penalties; link schemes evolved to outsmart the algorithm. New Penguin updates followed. The story went on for years, until it no longer made sense.
Voting 0