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HTML5 is the fifth major standard of HTML. Development of the standard began in 2007 and HTML5 websites started becoming mainstream in 2010. The final HTML5 standard was officially standardized by W3C on October 28, 2014.

The previous HTML standard, HTML 4.01, was standardized in 1999 – fifteen years before the HTML5 standard was published. However, in the decade preceding HTML5, most websites were written in XHTML, a more strict version of HTML published in 2000. HTML5 was designed to supersede both HTML 4 and XHTML by providing web developers with a simpler standard that includes several new features for the modern web.

The table below includes a list of new elements, or tags, introduced in HTML5 that are used to define the structure of a document.

<header>Defines the webpage header
<footer>Defines the page footer
<nav>Defines the navigation bar
<main>Defines the main content of a webpage
<article>Defines an article within a page
<section>Defines a section of a document or article
<aside>Defines content outside a page's primary content

These tags simplify the webpage's source as well as the corresponding CSS styles. For example, in order to define a navigation element in XHTML, you would typically write "<div class="nav"> in the page's HTML and define a class called ".nav" in CSS. In HTML5, you can simply insert the <nav> tag in the HTML and style the element itself using CSS.

HTML5 includes several other new tags as well. Examples include <canvas> and <svg> for graphics and <audio> and <video> for multimedia elements. These tags provide new capabilities for web developers, though it is important to note that HTML5 still relies heavily on CSS and JavaScript for page styling, animations, and user interaction. Therefore, most interactive HTML5 websites are built using a combination of HTML5, CSS3, and JavaScript or jQuery.

NOTE: Previous HTML standards included a space between the "HTML" and the number (i.e., HTML 1.0, HTML 4.01). HTML 5.0 does away with the space and is officially written as HTML5.

Updated: June 11, 2015

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