It is cross platform for designing and developing to work on pc,smartphone, laptop , tablet etc.

HTML5 is a cooperation the Web Hypertext
Application Technology Working Group (WHATWG)and between the World Wide Web Consortium (W3C).
WHATWG was working with web forms and applications, and W3C was working with XHTML 2.0.

HTML5 is the latest standard for HTML.

There are previous version of HTML, HTML 4.01, came in 1999, and the internet has changed significantly since then.

HTML5 was designed to replace both HTML 4, XHTML, and the HTML DOM Level 2.

It was programmed for the deliverabilty of extra plugins needed for music,movies,graphics,animation and web applications etc.

Why we use html5
Some rules for HTML5 were established:
New markups were introduced
New features based on HTML, CSS, DOM, and JavaScript were introduced.
New content-specific elements, like <article>, <footer>, <header>, <nav>, <section>

<canvas> element for 2D drawing
The <video> and <audio> elements for media playback
Support for local storage

New form controls, like calendar, date, time, email, url, searchHTML4/5 Reference

New Elements
2D/3D Graphics
Local Storage
Local SQL Database
Web Applications
New Attributes
Full CSS3 Support
Video and Audio
Browser Support for HTML5

All major browsers (Internet Explorer, Safari, Opera,Chrome, Firefox) support the new HTML5 elements and APIs, and continue to add new HTML5 features to their latest versions.

 

The HTML5 <!DOCTYPE>

In HTML5 there is only one DOCTYPE declaration, and it is very simple:
<!DOCTYPE html>

A Minimum HTML5 Document

Below is a simple HTML5 document, with the minimum of required tags:
<!DOCTYPE html>
<html>
<head>
<meta charset=”UTF-8″>
<title>Title of the document</title>
</head>

<body>
Content of the document……
</body>

</html>

HTML5 TUTORIAL