- XHTML combines XML and HTML 4 to provide developers with a language that conforms to the XML format, as opposed to HTML which is based on SGML. XML is much simpler to parse than SGML, and standards exist such as XSLT, XPath, and XQuery for manipulating XML documents. Unfortunately, support for XHTML in browsers is poor, with the leading browser, Microsoft Internet Explorer, not supporting the XHTML mime type 'application/xhtml+xml'.
- Extensible Markup Language (XML) is an extremely simple dialect of SGML. The goal is to enable generic SGML to be served, received, and processed on the Web in the way that is now possible with HTML. XML [XML] has been designed for ease of implementation and for interoperability with both SGML and HTML.
- Extensible Stylesheet Language, or XSL, is a language that describes how XML content is to be formatted.
- XUL( eXtensible User Interface Language; also 'XML-based User-Interface Language'), pronounced "Zool", is a standards-based language developed as a framework for executing applications within the Mozilla browser, just as you might run programs in the Java and .NET runtime environments.