Allows a website to define how a page is rendered in Internet Explorer 8, allowing a website to decide to use IE7 style rendering over IE8 rendering.
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
Google's hosted library for web fonts. Allows websites to choose and use fonts from a free, wide variety of fonts.
Sites who has this tag are verfied by google to use WebMaster tools