Few people have any idea what happens in the background when they click on an interactive Web page or use a Web application like Gmail. In this essay, Jesse James Garrett offers one of the clearest explanations we’ve seen of how developers are striving to create Web applications that feel and behave like desktop applications. Garrett, of the San Francisco Web design shop Adaptive Path, cites Gmail and Google Maps as examples of this new approach that he calls Ajax. It involves cobbling together several different technologies (Java, XML, etc.) in a way that allows the Web applications to be both powerful and responsive to users. The essay is a bit technical, but offers insight into the innovation happening at many companies in the valley.