Today, the European Organisation for Nuclear Research (CERN) will celebrate the 20th birthday of the worldwide web, an event that sparked a technology revolution.
Although the two words are widely thought to be interchangeable, it is important to distinguish the web from the internet, which has existed in various forms since the 1950s.
The internet defines a series of interconnected networks that allow data packets to travel, these days mostly using the TCP/IP transmission protocol, from one connected system to another.
The worldwide web, on the other hand, is more a network of content servers that allows information to be shared in specially formatted documents, hosted on systems connected to each other via the internet.
From humble beginnings as a proposal for a more effective document management system for internal use by Cern personnel, the web has grown exponentially into a global phenomenon, where almost a quarter of the world’s population convene to view and publish every type of information imaginable, and as a platform for communication, commercial transactions, dating, e-learning, entertainment, file swapping, software distribution and many other activities too numerous and diverse to list here.
So much so, that 20 years on, our reliance on the web for all, or the vast majority, of our information gathering has now become so complete that major internet outages that deny us access can quite literally bring our world to a crashing halt.
CERN has chosen Friday 13 March to mark the 20th anniversary of the day when one of its employees, Briton Tim Berners-Lee, first proposed a “universal linked information system” that would over the next few years develop into what we now know as the worldwide web.
It was designed to improve information management within CERN, then as now a large organisation employing several thousand people who all needed to communicate, share information, equipment and software.
Berners-Lee specified a number of clear, practical system requirements. One was remote access from computers running different operating systems.
At the time this included VM/CMS, Macintosh, VAX/VMS and Unix.
As well as providing search tools and access to existing databases, Berners-Lee also specified that systems should be allowed to link to each other without requiring any central control or co-ordination.
Furthermore, individuals were to be allowed to add their own private links, providing cross references (cross links) pertaining to authors, other documents, databases and information sources, within the browser itself to save duplication of information.
Berners-Lee realised that the human interface side of browsing through this complex information space was the key to its success, and acknowledged that an idea for the sort of system he envisaged had already been conceived hypertext (see 'Building blocks of the web', below).
Hypertext was proposed by Ted Nelson in 1963, then a computer programming student researching a document management system to index and organise his notes.
A variety of software applications using hypertext had already been developed, and Berners-Lee had experimented with hypertext as early as 1980.
Read on to page two for the genesis of the world wide web as we know it today.
In 1990, he refined his original 1989 proposal and co-developed a hypertext-based information management system with the help of another Cern employee, Robert Cailliau, calling it the worldwide web for the first time.
The system was based on an early form of Hypertext Markup Language (HTML) called HTML Tags, itself a derivative of Standard Generalised Markup Language (SGML), a specification for tagging elements in electronic documents defined in 1986.
HTML was not formalised until 1993 when the International Engineering Task Force (IETF) first proposed a specification, but many of Berners-Lee and Cailliau's original elements still survive in the language.
In 1991, an early WWW system was released to developers at research and academic institutes via the CERN program library. This included a simple HTML web browser, web server software, and a development library to help programmers build their own software.
According to CERN, the first web server in the US came online in December 1991 at the Stanford Linear Accelerator Center (SLAC) in California.
In 1993, the development kit was made generally available in the public domain, at which point the web's popularity really began to take off.
In the same year, the National Center for Supercomputing Applications at the University of Illinois released what many now regard as the precursor of the modern web browser.
The first version of Mosaic (later NetScape Navigator) was based on the X Window System and offered window-based interaction for the first time, with PC and Mac versions following shortly.
What followed was a rapid expansion in the number of web servers coming online and the number of people using web browsers to access the content those systems hosted.
The number of web servers rose from an estimated 250 by the end of 1993 to 2,500 by the end of 1994.
By 1995 it was estimated that up to 700 new web servers were coming online every day, and by the end of that year there were about 73,500 servers attached to the web. And it helped that, in the early days at least, both the web server development software and web browsers came free.
A recent report published by the International Telecommunications Union, an agency of the United Nations, estimated that almost a quarter of the world's 6.7bn population use the internet, with use more than doubling from 11 per cent in 2002.
It remains hard to imagine that either Berners-Lee or Cailliau could ever have envisaged that within 20 years of its inception, their invention would prove one of the most important technical revolutions of our time.
Building blocks of the web
HyperText Transfer Protocol (HTTP) is the network protocol used by the worldwide web.
When users click on a web link, the HTTP client in their browser opens up a port connection and then negotiates with the content/web server over wide area network links, transferring anything from text, images, sound and videos.
As content arrives, the browser's HyperText Markup Language (HTML) engine will start rendering the page - interpreting HTML code into how the web document page has been designed to look.
HTML syntax has changed little since Tim Berners-Lee's first description, made in late 1991.
In a document entitled "HTML Tags", he described 22 elements comprising the initial design of HTML, many of which are still in use today.