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In HTML5 First Look, author James Williamson introduces the newest HTML specification, providing a high-level overview of HTML5 in its current state, how it differs from HTML 4, the current level of support in various browsers and mobile devices, and how the specification might evolve in the future. Exercise files accompany the course.
One of the most basic questions asked about HTML5 is why do we need it? If HTML 4 provided such a stable foundation for the web and enjoys such widespread support, do we really need to change it? Well, the short answer is yes, but let's take a moment to explore the reasons behind the push for HTML5. Now, first, it's important to realize that contrary to popular belief, HTML5 is not attempting to reinvent the wheel. The specification for HTML5 is huge, over 900 pages long, and almost twice as long as the one for HTML 4.
Not all of that is dedicated to new features. One of the main reasons that HTML5 was favored over XHTML 2 was the fact that it remains backwards compatible with previous versions of HTML. That means that any user agent written to support HTML5 also has to support documents written in earlier versions of HTML. That doesn't sound like a big deal, but there are millions of HTML documents that are currently online that would suddenly stop working if backwards compatibility were not addressed. Now, the larger issue here is that earlier HTML specifications were rather vague about what to do with badly formed code.
This left error handling and parsing rules up to the user agents to figure out and implement. XHTML attempted to address this by adding stricter rules and in XHTML 2.0, draconian error handling that would stop rendering a page as soon as errors were detected. Now, a major part of the HTML5 specification attempts to deal with these issues. There are algorithms that define parsing rules for user agents that not only define how valid syntax should be parsed, but how errors should be handled as well.
Now, believe it or not, this level of detail is actually quite controversial. Some feel that HTML's role is to provide the syntax and allow the user agent to determine how the object model around that syntax should be created. Others feel that this level of detail will create a level of consistency across user agents that we've never seen before. Now, theoretically, it's going to allow designers and developers to write HTML without worrying about the differences between user agents or even devices. Now, in truth, whether it works or not is largely up to how the specification will be adopted by those that choose to support it.
Now, of course, there are many new features in HTML5 that attempt to address how the web has evolved over the last decade or so. New semantic elements like the section and article tags will give pages additional structure and meaning, especially helpful for blogs and other applications. Now, speaking of applications, at first glance, items like APIs, local storage, and support for video and audio seem radical when introduced into an HTML specification. The truth however is that this simply reflects the needs of modern web design.
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