XHTML - Extensible Hypertext Markup Language
XHTML is a further evolution of HTML as an XML vocabulary. This evolutionary step eliminated problems that arose from the existence of proprietary, inconsistent or badly coded HTML web pages. With XHTML, HTML coding is used but it follows XML standards. XHTML web pages look similar to HTML pages, except since XML standards are followed, the tags have a closing tag and the tags are nested properly, attributes are quoted, and there is a root tag for the overall web page. The goal of using XHTML along with CSS is to bifurcate the display and presentation tags (CSS) from the web page structure (XHTML).
XML - Extensible Markup Language
XML is an ISO-compliant language that enables a more efficient and organized delivery of data and information over the Internet.
XML Sitemap
An XML sitemap is used by search engines, especially Google, to aid in indexing a website. The XML sitemap lists the internal pages and can assign values for how often the page is updated and importance of the page based on a sliding 1 - 10 scale.
