This element contains the whole web page. It is the root element of an HTML document; all other elements are contained in this. It delimits the beginning and the end of an HTML document and was standardized in HTML 2.0. In XHTML document it is after optional XML and required DOCTYPE declaration. It has an opening <html> tag and ends the document with a closing </html> tag.
In strict XHTML, opening tag must have a namespace identifier attribute to indicate that the markup in web page belongs to the XHTML 1.0 namespace and is given as
In older HTML version, a version attribute indicated version of HTML web page is in, but not used now. XHTML pages should use DOCTYPE declaration and the xmlns attribute to specify version of XHTML used.