LinkedIn Plugins are a way to drop LinkedIn functionality into websites.
Google+ platform websites integration using the Google+ platform tag.
The Tweet Button is a small widget which allows visitors to share content and connect on Twitter.
Let visitors recommend your content on Google Search and share it on Google+.
This site uses the viewport meta tag which means the content may be optimized for mobile content.
Open graph description entity tag
Sites who has this tag are verfied by google to use WebMaster tools