In the 1990s, client/server was the predominant architecture used to build business applications. The applications had rich functionality, were responsive, and satisfied users' needs. Client/server worked in a time where the only networks were the ones owned and controlled by the enterprise—and the only user base was internal.
As web technologies emerged, client/server lost favor to thin client HTML architectures because it requires no downloads, has no distribution issues, and works over firewalls. However, page-oriented Web applications are, in general, not rich, not responsive, and do not satisfy
users' needs. While users like the ability to run applications from anywhere on any platform—they are unsatisfied with the user experience.
Today, the web development world is buzzing with the terms Rich Internet Applications and AJAX. The use of AJAX techniques allows developers to build Rich Internet Applications that deliver both the functionality and the richness of client/server applications as well as the ubiquity and accessibility of the web.