Changes in HTML 5 - <header> Tag
What's new in HTML 5
The <header> tag is one of the new elements in HTML 5. It is one of the new sectioning tags in HTML 5, which are intended to reduce the need to use <div> tags for sectioning purposes.
Differences between HTML 5 and earlier versions of HTML
The <header> tag did not exist in older versions of HTML.
The 2000-2010 Recommendations from the W3C HTML Working Group defined the HTML namespace for the names of all HTML element types, which now includes the header element name. In older (pre-2000) versions of HTML, element type names were not associated with a namespace.