Introduction

THE BASIC TECHNOLOGIES BEHIND THE WEB are now almost a quarter of a century old. HTML dates all the way back to 1993, the same year the first popular web browser, Mosaic, appeared on the scene.

You may have thought, therefore, that the technologies behind the Web would have entered a comfortable middle-age—still improving around the edges maybe—but not innovating with the pace and excitement of their early years.

In fact, nothing could be further from the truth. The last ten years have been some of the most ­exciting and innovative in the history of the Web, and this pace of change is continuing to ­accelerate. As a result, the Web is no longer the preserve of simple “websites.” It is the realm of “web ­applications”: feature-rich applications that just happen to run inside web browsers.

A whole new class of computing devices has accentuated the pace of this change. Web browsers are no longer the preserve of desktops and laptops: They now appear on a myriad of devices from smart phones to smart TVs. The fact that web browsers are the one universal feature across these diverse devices has served to enhance the appeal of browser-based web applications: You write the web application once, and your users use it from any device they choose.

This innovation of the last decade did not happen by accident. Various standards committees have been hard at work for more than a decade devising a set of standards that have been grouped under the umbrella of “HTML5.” These standards ...

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