The first version of HTTP, HTTP/0.9 was released in 1991. However, this was not an official release. This protocol was simple and was used to transfer raw data over the Internet. The Web servers that accepted HTTP requests at that time responded to simple requests such as this one:
In this scenario, if a file with the name index.html were in the document root (the directory that stores the Web site-related files) of the Web server, the contents would be displayed on a Web page. If such a file were not found, the Web server would respond with an error. It was not long before this version became obsolete, and in May 1996 Request For Comments (RFC) for HTTP 1.0 was released. A new feature was incorporated into this release. This version of HTTP used headers. Headers are pieces of text that are attached to data packets and that describe the data being transported. The most common header looks something like this:
This header indicates that the data being transported is text that is marked up using HTML. Before sending requests to the Web server, the browser attaches headers to the data packets. The latest version of HTTP is HTTP/1.1. This version was officially announced in June 1999 with the release of RFC 2616.