The acronym Ajax stands for Asynchronous Javascript and XML. Its various potted histories identify the author of the term as Jesse James Garret, in February 2005. It describes a group of technologies which are employed to improve the front-end usability of web applications, primarily by replacing obvious postbacks and screen refreshes with ‘background’ calls to the server and scripted page updates.
ASP.NET Ajax is Microsoft’s implementation of an Ajax library for ASP.NET 2.0. Unlike many of the AJAX libraries available it provides integrated server-side libraries and client-side libraries.
It is worth pointing out from the outset that a fair amount of what is bundled into this library doesn’t really merit the term Ajax as desecribed above, since it deals only with client-side functionality or design. It seems to me that ASP.NET Ajax project involves the techological descendents of both ‘Remote Scripting’, whereby calls are made back to the server without page refreshes, and ‘DHTML Behaviors’, whereby client-side objects are built out of a mix of HTML, CSS and Javascript. The term ‘Ajax’ is more obviously associated with the former.
This series of pages was put together for the other developers at my work, most of whom were aware of Ajax but not the specific details of ASP.NET Ajax. It is a mix of high-level overview of the capacities of this library, plus some more detailed practical advice. Although I have done my best in the time available to make it accurate, it may contain errors.