nginx [engine x] is a HTTP server and mail proxy server written by Igor Sysoev.
Sites who has this tag are verfied by google to use WebMaster tools
The http-equiv attribute provides an HTTP header for the information/value of the content attribute. The http-equiv attribute can be used to simulate an HTTP response header.
Meta Keywords are a specific type of meta tag that appear in the HTML code of a Web page and help tell search engines what the topic of the page is.