Changes in HTML 5 - <rt> Tag

What's new in HTML 5

The <rt> tag is one of the new elements in HTML 5.

Differences between HTML 5 and earlier versions of HTML

The <rt> 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 rt element name. In older (pre-2000) versions of HTML, element type names were not associated with a namespace.