You cannot use block level elements inside a definition term. The description list (HTML5 dl) is similar, but allows both dt and dd elements. Try and test HTML code online in a simple and easy way using our free HTML editor and see the results in real-time. HTML 4.01 Strict html4-trans HTML 4.01 Transitional html4-frame HTML 4.01 Frameset html5 (default) HTML5 xhtml-strict XHTML 1.0 Strict xhtml-trans XHTML 1.0 Transitional xhtml-frame XHTML 1.0 Frameset xhtml11 XHTML 1.1 Microsoft Windows, HP-UX). Tag Name Code Example Browser View