XUL

XUL (pronounced zool ), the XML User Interface Language, is an XML user interface markup language developed by the Mozilla project for use in its cross-platform applications, such as Firefox. The only complete implementation of XUL is the Gecko layout engine.XUL relies on multiple existing web standards and technologies, including CSS, JavaScript, and DOM, which makes it relatively easy to learn for people with a background in web programming and design. XUL and web developer documentation is available from the Mozilla Developer Center [1].XUL has no formal specification or interoperable non-Gecko implementations and therefore may be described as an internal or proprietary language. On the other hand, its implementation (Gecko) is open source and Mozilla provides experimental XULRunner builds to let developers build their applications on top of the Mozilla application framework and XUL in particular.
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XML User-Interface Language