How can I stop other sites from accessing my Facebook?

[Fiddlesticks]

I was reading an article the other day, when I saw an area of my screen which I have never noticed before..." Friends that have read this article."

I can only guess that Yahoo! is accessing my Facebook and I don't really want that, is there any way to block every site except Facebook of course, from accessing my profile?

[CanadaRAM]

You really expect Facebook not to sell your information?

Anything which is publicly viewable on Facebook can be viewed by robots and search engines to.
You can make all of your posts Friends only

In your privacy settings make sure you have
Do you want other search engines to link to your timeline? set to Off

and In your Timeline and Tagging
Who can see things on my timeline? set to Friends or Friends except Acquaintances
When you're tagged in a post, set to Only Me