XHTML

XHTML (Extensible HyperText Markup Language) is a family of W3C specifications that reformulated HTML as an XML application, requiring stricter syntax rules such as properly nested elements, lowercase tag names, and quoted attribute values. XHTML 1.0, published in 2000, was essentially HTML 4.01 rewritten in XML syntax. XHTML 2.0 was a more ambitious effort to create a semantically richer markup language with features like the role attribute for explicit semantic annotation, but it was never completed and was abandoned in favor of HTML5. For accessibility, XHTML promoted cleaner, well-structured markup that was easier for assistive technologies to parse, and the XHTML 2.0 effort helped incubate ideas — like structural roles and separation of content from presentation — that influenced both HTML5 and WAI-ARIA.