Some of the elements listed below have been deprecated and are not included in the HTML / XTHML specification. Depending on the HTML/XHTML Doctype (DTD – Strict, Transitional, or Frameset), some elements may or may not be supported. It is recommended that you do not use HTML elements that are deprecated because they may become obsolete in future versions of browsers. Developing your pages in XHTML with a strict Doctype will ensure the most compatibility across browsers.