Google APIs are application programming interfaces developed by Google which allow communication with Google Services and their integration to other services.
Content Security Policy is best used as defense-in-depth, to reduce the harm caused by content injection attacks.
Sites who has this tag are verfied by google to use WebMaster tools
This tag indicates websites that a chrome application.
The Open Graph protocol enables any web page to become a rich object in a social graph, a open protocol supported by Facebook
Google's hosted library for web fonts. Allows websites to choose and use fonts from a free, wide variety of fonts.