How does facebook know what I am googling or searching for outside of facebook?

[A to the Awesome!]

Every now and then I will glance over to the advertisements that are designed to market specifically to me and my interests. I understand why they have a golf ad (because in my interests section I have "golfing") and I also understand why there is a Metallica add, (in my music part of my info section i have "Metallica") but recently I have found that my recent searches are turning into adds on my facebook page... and they are extremely specific so I KNOW it isn't a coincidence. My question is this, How does facebook know what I am searching for?

[Zeux]

cookies left on your computer by other pages.. some ppl freak out about them. others dont care. as long as you clear them out when you're done browsing you'll be fine.

[☮hola☮]

because google runs 90% of the advertising so it's not facebook it's google that knows what your Googleing

[gido]

Because you tell them the true.
Internet is not internet of 10 years ago nomore. It is dangereous now, Plenty of search engines, spyware, and more are looking for information about users. Advertisers and more pay money for information about us. So you have to lie. you come on facebook or you are making a new accoutn somewher else: they ask your gender, name, second name....... so you should not tell them the true: if you are male then mark 'female' if your name is like frank obama then make it jack russel for example . The advertise they send to you specific is because they know who you are, your age, your interest and so on.
Be carefull on internet and all those social sites are the most big danger off all.

[Ivolution]

Your hunch is incorrect, search information is not shared in that way.

Currently (September 2009), Facebook does not have any arrangement with Google or any other search engine that gives it or advertisers access to your search data.

How Facebook ads work is very specific and defined in detail on the site. Ads take advantage of user's willingness to share (usually) true information about themselves, such as gender, location, age, and even their marital status. Advertisers can select from a specific range of these, but they are all from within Facebook. As an advertiser, I can target, for example, users who list "model airplanes" in their interests or are a member of 1940 Biplane Club on Facebook, but I am not given the option to target based on searches or external sites such as Google.

(By the way, user information is not given to advertisers; the targeting is done by an automatic and anonymous system.)

See the source link for more information on how exactly Facebook ads work.