HTML5

What do we mean by HTML5?:

This might sound like a silly question, but there is an increasing tendency amongst standards punditsto lump all exciting new web technologies into a box labeled HTML5. So, for example,we’veseen SVG (Scalable Vector Graphics) referred to as “oneof the HTML5 family of technologies,” even though it’s an independent W3C graphics spec that’s 6 years old.Further confusion arises from the fact that the official W3C specis something like an amoeba: Bits split off and become their own specifi cations, such as Web Sockets or Web Storage (albeit from the sameWorking Group, with the same editors).So what we mean in this book is “HTML5 and related specifi cationsthat came from the WHATWG “ (more about this exciting acronym soon). We’re also bringing a “plus one” to the party—Geolocation—which has nothing to do with our defi nition of HTML5, but we include simply for the reason that it’s really cool,we’re excited about it, and it’s part of the New Wave of Exciting Technologies for Making Web Apps.

Who? What? When? Why? A short history of HTML5:

History sections in computer books usually annoy us. You don’t need to know about ARPANET or the history of HTTP to understand how to write a new language. Nonetheless, it’s useful to understand how HTML5 came about, because it will help you understand why some aspects of HTML5 are as they are, and hopefully pre-empt (or at least soothe) some of those “WTF? Why did they design it like that?” moments.

What about XML?:

HTML5 is not an XML language (it’s not even an SGML language, if that means anything important to you). It must be served as text/html. If, however, you need to use XML, there is an XML serialisation called XHTML5. This allows all the same features, but (unsurprisingly) requires a more rigid syntax (if you’re used to coding XHTML, this is exactly the same as you already write). It must be well-formed XML and it must be served with an XML MIME type, even though Internet Explorer 8 and its antecedents can’t process it (it offers it for downloading rather than rendering it). Because of this, we are using HTML rather than XHTML syntax in this book.

HTML5 support:

HTML5 is moving very fast now, and even though the spec went to fi rst fi nal draft in October 2009, browsers were already implementing HTML5 support (particularly around the APIs) before
this date. Equally, HTML5 support is going to continuously increase as the browsers start rolling out the features. This book has been written between November 2009 and May
2010. We’ve already amended chapters several times to take into account changes in the specification, which is looking (dare we say it?) pretty stable now. (We will regret writing that, we know!) Of course, instances where we say “this is only supported in browser X” will rapidly date—which is a good thing.

Let’s get our hands dirty:

So that’s your history lesson, with a bit of philosophy thrown in. It’s why HTML5 sometimes willfully disagrees with other specifications— for backwards-compatibility, it often defines what browsers actually do, rather than what an RFC specifies they ought to do.
It’s why sometimes HTML5 seems like a kludge or a compromise— it is. And if that’s the price we have to pay for an interoperable open Web, then your authors say “viva pragmatism!” Got your seatbelt on?