Philip K. Dick wrote over a hundred short stories, none better than "The Minority Report", where police were able to anticipate crimes rather than arrest people after the fact - leading to arrests before the fact for crimes people hadn't committed yet and a 1950s science-fiction discourse on the nature of free will.

In "The Minority Report" three unaccountable mutants sit in a room mumbling gibberish until a computer sifts through it and makes projections about parallel futures created by actions; when two predictions agree it is a majority report.  When a police commissioner finds out he is going to be arrested for a future murder, he goes out to find the minority report where he commits no crime.

Google wants to do the same thing, except without the mutants, and they want to predict your future web browsing rather than crime.   Web prediction is being tested in Google Chrome and features 'pre-rendering', which is like precognition, but Google guessing which pages you'll visit next is likely to be fairly accurate, since they have all of the data and it may be gibberish to you and me, but they seem to have figured out what to do with it, even when it's bad.

Is it accurate now?   Not especially, say testers, but they also aren't the general population.    The future is always diverging and if you're using a tool designed to predict your future you will trip it up, consciously or not.