XHTML means Extensible HyperText Markup Language and is an extension of HTML file type. It is used as a markup language particularly for websites. It has all the functionalities of HTML files but uses a stricter syntax. This is because HTML is based on the flexible SGML where as XHTML is based on XML, a more restrictive subset of SGML. Due to the stricter syntax of XML documents this file type can be more easily processed by an XML parser while normal SGML documents require a much more complex parser. The XHTML 1.0 became a W3C standard on January 26, 2000.
MIME TYPE: application/xhtml+xml