The document discusses building web applications using a front-end UI layer with HTML, CSS, and JavaScript for presentation and navigation. An application layer with additional JavaScript implements data services to retrieve and manipulate data in JSON or XML formats from a back-end data access layer. This architecture allows web apps to be built richer by reaching more clients across servers and browsers through programmable APIs over HTTP. Statistics are provided on growth in the number of available APIs. Contact details are given to learn more.