Keep-Alive for 30 secs

   The Keep-Alive general header allows the sender to hint about how the connection may be used to set a timeout and a maximum amount of requests.

Vary Header Accept-Encoding

   The Accept-Encoding request HTTP header advertises which content encoding, usually a compression algorithm, the client is able to understand. Using content negotiation, the server selects one of the proposals, uses it and informs the client of its choice with the Content-Encoding response header.

Nginx

   Nginx is a web server which can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache. The software was created by Igor Sysoev and first publicly released in 2004. A company of the same name was founded in 2011 to provide support and Nginx plus paid software.

Google Hosted Libraries

   The Google Hosted Libraries is a stable, reliable, high-speed, globally available content distribution network for the most popular, open-source JavaScript libraries.

jquery 1.7.1

   JavaScript library for DOM operations

SPF

   The Sender Policy Framework (SPF) is an email-authentication technique which is used to prevent spammers from sending messages on behalf of your domain. With SPF an organisation can publish authorized mail servers.

PHP 5.6.38

   PHP: Hypertext Preprocessor is a general-purpose programming language originally designed for web development.

Chunked transfer encoding

   Chunked transfer encoding is a streaming data transfer mechanism available in version 1.1 of the Hypertext Transfer Protocol (HTTP). In chunked transfer encoding, the data stream is divided into a series of non-overlapping "chunks"