A Software Engineer Learns HTML5, JavaScript and jQuery: A guide to standards-based web applications

4 May 2014: New revision is now available. Fully revised and re-edited.
HTML5 web applications are now capable of matching or exceeding the scale and sophistication of desktop applications, but with the unique advantage of running natively inside the web browsers on billions of desktop computers, phones, TVs and tablets.
This revolution (or more correctly – evolution) has happened for a number of reasons:
Browsers have introduced new standards-based APIs allowing web applications to (amongst other things) store data offline, retrieve data from the server dynamically, spawn background processes and interact with the filesystem.
Software engineers and programmers have begun to think of the much maligned javascript language in a new light, and unlock its potential as a rich and expressive language capable of producing large scale, well-structured applications.
The jQuery library has eased the pain of interacting with Document Object Model, and therefore writing applications that dynamically respond to user interaction.
The HTML markup language has been overhauled and extended to provide more semantic meaning, and many additional elements and attributes.