Stands for Extensible Hypertext Markup Language, a proposed version of Hypertext Markup Language (HTML) from the World Wide Web Consortium (W3C). XHTML 1 is basically a reformulation of HTML 4 in Extensible Markup Language (XML) and can smooth the migration from HTML to XML by allowing developers to create HTML documents that contain XML functions.
The advantages of using XHTML instead of HTML for Web content development include the following:
Web sites can already be migrated to XHTML because XHTML conforms to existing Hypertext Transfer Protocol (HTTP) user agents (Web browsers). Migrating ensures that content is XML-conforming, which is advantageous because XML is the future Web content paradigm.