Flex applications have a default visual appearance that's determined by a combination of graphics that are embedded in the Flex framework, known as skins, and various visual settings that are set through Cascading Style Sheet declarations.
Web site developers may already be familiar with the concept of Cascading Style Sheets (CSS), because this technology has been increasingly used to control the visual appearance of Web pages since its introduction in 1996.
The Cascading Style Sheet recommendation is created and published by the World Wide Web Consortium (W3C), the same organization that publishes the recommendations for HTML, XML, and other critical Internet technologies.
Information about the World Wide Web Consortium's CSS recommendation and other CSS resources is available at
It's up to the vendors who actually create the Web browsers and other products to implement CSS for their own platforms. Web browsers, for example, implement various subsets of the W3C recommendation; it's only in recent years that the major browsers such as Internet Explorer and Firefox have approached compatibility in their CSS implementations.
The use of CSS to control visual appearance isn't limited to Web-based technologies. Flex applications that are installed on the desktop with the Adobe Integrated Runtime (AIR) use CSS in exactly the same manner as Flex Web applications.
The Flex framework implements ...