Ajax is no longer an experimental approach to website development, but the key to building browser-based applications that form the cornerstone of Web 2.0. Head First Ajax gives you an up-to-date perspective that lets you see exactly what you can do—and has been done—with Ajax. With it, you get a highly practical, in-depth, and mature view of what is now a mature development approach.
Head First Ajax covers:
Making Ajax requests with XMLHTTPREQUEST objects
The asynchronous application model
The Document Object Model (DOM)
Controlling the browser with the Browser Object Model
XML Syntax and the XML DOM tree
XML Requests & Responses
JSON -- an alternative to XML
Ajax architecture & patterns
The Prototype Library
The book also discusses the server-side implications of building Ajax applications, and uses a "black box" approach to server-side components.