Introduction to HTML

HyperText Markup Language, usually called HTML for short, is the standard language for creating web pages. HTML, along with CSS and JavaScript, is one of the fundamental technologies used to create web pages, web applications, and other user interfaces. Web browsers read HTML files and display them visually or read the audibly. HTML describes the content and semantic structure of a website, which makes it a markup language, rather than a programming language. (It also can include cues for the appearance of a website, although this role has been taken over by CSS.)

The basic units that make up a web page are HTML elements. HTML elements can describe structural elements of a body of text such as paragraphs, lists, links, quotes, and more. HTML elements can also describe interactive forms, or embedded objects like images. These elements are represented in an HTML file by tags, demarcated by angle brackets. Some tags stand by themselves, such as img and input. Many tags, such as <p>...</p> surround text and other tags, and provide information about the content inside. Browsers do not directly display HTML tags. Instead, the browser uses them as clues for how to correctly display the rest of the page.

HTML can reference outside files as well. JavaScript can provide interactive behavior for web pages. CSS can alter the style and layout of a page. For the last few years, this has been the preferred way to control the look of web pages, according to the World Wide Web Consortium (W3C), which maintains both the HTML and the CSS standards.

History of HTML

Tim Berners-Lee was working as a contractor at CERN in 1980 when he suggested and built a system for researchers to use and share documents, which was called ENQUIRE. He proposed in 1989 an internet-based system built around a concept he called hypertext. In late 1990 he wrote the first specification for HTML and created a web browser and server. That year he and a CERN data systems engineer named Robert Cailliau wrote a request for funding, but CERN did not formally adopt the project.

HTML was first publicly described in a document titled “HTML Tags”, published on the Internet by Berners-Lee in late 1991. This document listed eighteen different elements that made up the first HTML specification. All of them, except for the hyperlink tag, were based on SGMLguid, an in-house documentation format used at CERN, which was in turn based on the Standard Generalized Markup Language (SGML). Eleven of the eighteen original elements are still part of the HTML 4 standard.

Berners-Lee described HTML as a form of SGML. The first official proposal for an HTML specification, published by the Internet Engineering Task Force (IETF) in 1993, formally defined HTML as a type of SGML. The proposal described the grammar of HTML with an SGML Document Type Definition.

The IETF formed an HTML Working Group in early 1994. In 1995, the group completed the HTML 2.0 specification, which was the first HTML specification explicitly designed as a standard that future implementations should be based on. Conflict within the IETF halted further development, and the HTML standard was taken over by the World Wide Web Consortium (W3C) in 1996. With input from commercial software vendors, the W3C published several new versions, including HTML 4.01 in late 1999. HTML also became the international standard ISO/IEC 15445:2000 in 2000. The competing group WHATWG (Web Hypertext Application Technology Working Group) started developing HTML5 in 2004. The W3C started collaborating with WHATWG on HTML5 in 2008, the final standard of which was completed in late 2014.