HTML5: from documents to applications - HTML5 in Action - page 3

By the end of this chapter, you'll have a broad sense of what HTML5 has to offer and be
able to use it in your own web applications.
Documents (HTML4) versus applications (HTML5)
Initially the web was all about documents. Forms were added by the Mosaic browser in
1993, but this was merely data entry; all application logic remained on the server. The in-
troduction of JavaScript in 1995 made browser-based applications theoretically possible,
but things didn't really take off until after the arrival of the XMLHTTPRequest object in
1999. The last major version of the HTML specification, 4.01, only became a recommend-
ation in 1999. So it's not surprising that the 4.01 spec still concentrated almost entirely
on the use of markup to describe documents, what we now normally refer to as semantic
markup .
The next version of HTML has been a long time coming, and the web has changed a
lot in the meantime. As you'll see in the following sections, HTML5 contains improve-
ments in the area of semantic markup. The majority of the differences and improvements
in HTML5 over HTML4, however, are in facilities for building browser-based applications
with JavaScript. Because of that, and because this topic is focused on the new features of
HTML5, we spend a lot more time dealing with JavaScript than with markup. We do cover
some markup, but, as you'll see, JavaScript is the real big deal in HTML5.
To get started, we'll show you how to get up and running by creating an HTML5 document.
1.1. Exploring the markup: a whirlwind tour of HTML5
The best way to learn what's new in HTML5 is to jump right in and explore. The goal of
this section isn't only to give you a high-level tour of the new features but also to give you
enough knowledge to be able to update your existing applications to use HTML5 conven-
tions, without upsetting users who don't have the latest and greatest browsers.
In this section, you'll learn
• How to create a basic HTML5 document structure.