How do a code html frames?

XHTML is the successor to HTML 4.01; XHTML 1.0 supports the same elements as HTML 4 and in most cases valid XHTML 1.0 documents will be valid or nearly valid HTML 4 documents. XHTML 1.0 migrates HTML from its SGML underpinnings to an XML foundation. Accordingly, the discussion of elements within this article focuses on the final SGML based HTML, version 4.01 (unless noted otherwise). However, to the extent that XHTML 1.0 elements remain identical to the HTML 4.01 elements, the discussion remains applicable (see HTML for a discussion of the minor differences in content between XHTML 1.0 and HTML 4.01).