An XHTML document must have a DOCTYPE declaration, as well as the <html>, <head>, <title>, and <body> elements. (In HTML, you can omit the <html>, <head>, and <body> elements.) The xmlns attribute in the <html> tag must specify the xml namespace for the document. The namespace for XHTML is defined to be http://www.w3.org/1999/xhtml.
This example shows an XHTML document with a minimum of required tags:
