Quote:

> They had an ad from an online airfare site...and it was proposing that I look for fares to and from where I live to a city I've booked flights for before. How did they know? I can't believe it was coincidence.

cookies.



The "from" part is even easier than that since the site has to have your IP address so (unless you use some sort of proxy) they can easily look up where your ISP is. Even if you have a national ISP, they use specific IP ranges in specific markets. The "to" could just be a coincidence unless you travel to odd places.