As the Internet has become more mature, rich applications featuring responsive user interfaces and interactive capabilities have become increasingly popular. The capabilities represent a way to make programs easier to use and more functional, thus enhancing the user experience. Developers have used a variety of applications from companies, such as Macromedia, Microsoft, and Sun Microsystems, to add these capabilities in the past. However, Web applications have generally exhibited problems such as slow performance and limited interactivity, particularly when compared to typical desktop applications, noted Nate Root, research director for Forrester Research, a market analysis firm.

XML is a markup meta language that can define a set of languages for use with structured data in online documents. Any organization can develop an XML-based language with its own set of markup tags.

Cascading Style Sheets (CSS) is a W3C standard since 1996. CSS gives Web site developers and users more control over how browsers display pages. Developers use CSS to create stylesheets that define how different page elements, such as headers and links, appear. Multiple stylesheets can apply to the same Web page.