Different Versions of HTML5
HTML’s primary job is to label and accommodate content on web pages. But HTML comes in various versions, each of which handles content, but each of which is slightly different from the other. The basic rules and components stay more or less the same, but some important details differ.
HTML stands for HyperText Markup Language, markup developed in the late 1980s and early 1990s to describe web pages. HTML is now enshrined in numerous standard descriptions called specifications from the World Wide Web Consortium (W3C) and the Web HyperText Application Technology Working Group (WHATWG). Work on HTML specifications for versions 1 – 4 ended in 1999.
When you add an X in front of HTML, you get XHTML, a reworked version of HTML based on the eXtensible Markup Language (XML). XML was designed to work and behave well with computers, software, and the Internet.
The original versions (1 – 4, that is) of HTML included some irregularities that could cause heartburn for software that reads HTML documents. XHTML was designed to use an extremely regular and predictable syntax that’s easier for software to handle.
XHTML was supposed to replace HTML, but increasing technical complexity in later versions caused it to fall by the wayside. (XHTML 2.0 was so complicated, it was neither widely adopted nor used very much at all.)
In 2004, the WHATWG began work on what is called a Living Standard for what is called HTML5 today. Some areas of HTML5 are still under development or subject to unresolved controversy.
HTML5 already appears to be succeeding where XHTML did not. Even though the standard is still under construction, HTML5 is widely adopted and used on the web today. In fact, the HTML5 specification is in what’s called Candidate Recommendation form as of December 2012. That’s one step before final Recommendation status is reached; most experts expect that final version to be approved and ratified in late 2013 or early 2014.