Facebook Connect allow users to connect their Facebook identity, friends and, privacy to any website. Facebook Connect is Facebook's first attempt to allow access to Facebook user data outside of Facebook itself. The company is describing it as giving third party applications access to much of the same data as Facebook applicat...
Content Security Policy is best used as defense-in-depth, to reduce the harm caused by content injection attacks.
Open graph description entity tag
The Open Graph protocol enables any web page to become a rich object in a social graph, a open protocol supported by Facebook
Sites who has this tag are verfied by google to use WebMaster tools