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In the ten years or so since I made my first static web page, its been amazing to see the evolution of the Web as a platformfirst for the exchange of information, and then for actual applications, running right in the browser. And now the AJAX explosion is taking web development to the next level. Using the power of AJAX-style development, you can create applications that rival desktop apps in their power and responsiveness and, best of all, you dont have to rely on ugly hacks and kludges to get there.

What is AJAX? The acronym originally stood for Asynchronous JavaScript and XMLquite a mouthfulbut it has since come to refer to a style of development that uses web technologies like XML, DOM, CSS, and JavaScript to create uber-interactive web documents that behave like full-blown applications. None of these AJAX technologies are actually all that new (even the AJAX secret sauce, XMLHttpRequest, has been around for years), but not a lot of people really knew how to use them to the fullest. Now, with the proliferation of Web 2.0 applications that push the web-app envelope, and its cool, easy-to-remember name, the AJAX style of development is really starting to take off.

In the early days, web apps used server-side scripting like CGI, as well as simple web forms and image rollovers in the browser. Now were seeing developers take major steps forward to enhance the user experience with the ability to update the UI in pieces, instead of requiring a single, enormous redraw, and client-side functionality like drag-and-drop and edit-in-place. Todays web applications are more interconnected as well, and are sometimes made up of data from multiple services or sources. A browser-based AJAX app is a fantastic platform for providing this kind of super-interactive, networked app experience to users. And the best part is that the AJAX revolution is still just getting started, so nows a great time to jump in.

This book gives me a chance to show some cool ways in which you can use AJAX techniques to add real power and responsiveness to your web applications while supporting accessibility and backward compatibility. The beauty of AJAX is that it lets you do all this using straightforward, standards-based code, so you wont be seeing weird hacks or browser-specific code in this book. So, roll up your sleevesI hope youre ready to get your hands dirty in some AJAX code!

This book is aimed primarily at web application developers who are already familiar with basic client-side web technologies like CSS and JavaScript.

If thats not you, dont be put off: this book will suit you if youre willing to do some learning as you go. JavaScript syntax is pretty straightforward, and were using plain, vanilla code thats pretty much free of browser-specific workarounds. We also provide links to valuable resources that you can use to learn more about the technologies used in AJAX development.

Some traditional applications programmers may also find this book of interest for seeing how they can create a real desktop-app-style user interface that runs in a browser. More and more of these guys will be looking to dip their toes into the AJAX pool as web application development and plain application development continue to converge.

This book contains eight chapters. Each chapter builds on the concepts and techniques introduced in the previous ones, so if youre still fairly new to web development, youre probably better off to take the chapters step by step, in order. If youre a battle-hardened veteran, it might make more sense for you to jump around among the topics that interest you.