Websites using some form of Captcha technology on them.
Anti-bot CAPTCHA widget that helps digitize books by providing snippets of books for people to enter the text for. Owned by Google.
This site uses the viewport meta tag which means the content may be optimized for mobile content.
PayPal is a American international e-commerce service that enables companies and individuals to send money and to accept payments without revealing any financial details.
CloudFlare is a global CDN and DNS provider that can speed up and protect any site online.
Google APIs are application programming interfaces developed by Google which allow communication with Google Services and their integration to other services.
nginx [engine x] is a HTTP server and mail proxy server written by Igor Sysoev.
UTF-8 (8-bit UCS/Unicode Transformation Format) is a variable-length character encoding for Unicode. It is the preferred encoding for web pages.
Sites who has this tag are verfied by google to use WebMaster tools
A canonical link element is an HTML element that helps webmasters prevent duplicate content issues by specifying the "canonical", or "preferred".
Google's hosted library for web fonts. Allows websites to choose and use fonts from a free, wide variety of fonts.