Hyper Text Transfer Protocol

HTTP was originally defined in RFC 1945. HTTP 1.1 is in RFC 2616.
HTTP is a stateless protocol for fetching MIME-encoded information from another machine in the Internet.

The steps are:

Make connection.

Make request:

GET /index.html HTTP1.0
Accept: text/html, text/plain //optional
User-Agent: Mozilla/1.0 //optional
\r\n
\r\n

A POST request can include data before the

\r\n\r\n

Get a response:

HTTP/1.1 200 OK //response code
Date: Fri, 28 Dec 2001 14:59:11 GMT
Server: Apache/1.3.20 (Unix) PHP/4.0.6 mod_ssl/2.8.4 OpenSSL/0.9.6b
Last-Modified: Fri, 28 Dec 2001 14:55:00 GMT
ETag: "a5a99-17f5-3c2c87c4" //entity tag
Accept-Ranges: bytes
Content-Length: 6133
Connection: close //one-shot
Content-Type: text/html
\r\n
\r\n
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<HTML LANG="en"><HEAD>
<TITLE>University of South Carolina Home Page</TITLE></HEAD>
......

Close connection.

Closing the connection every time is costly. HTTP 1.1 does not close the connection.
Cookies are opaque strings that are sent by the browser to the server based on its IP number.
Under the Common Gateway Interface (CGI) the server rather than returning the named file will run it as a program, passing it the arguments and values in the URL path.