HTML and CSS Reference
HTML and XHTML
This chapter provides a complete reference for the elements in the HTML 4.01 and
XHTML 1.0 specifications. All known HTML5 elements at the time of this edition's
writing are covered as well, but given the fluid nature of the specification, some
elements may have been omitted or syntax may have changed by the time of publication.
You are encouraged to proceed with caution when considering the HTML5 information
because, again at the time of this writing, the specification is in flux and few of the elements
discussed work natively in browsers. Proprietary features discussed in this reference also
should be treated with some caution. All the browser-specific elements and attributes
supported by Internet Explorer, Firefox, Safari, Chrome, Netscape, and Opera are presented.
Some elements presented in the reference might be deprecated, but they are included
nevertheless either because browser vendors continue to support them or because they may
still be found in use.
Flavors of HTML and XHTML
There are many versions of HTML and XHTML in existence (see Table 3-1). In the early
days, the specification of HTML was somewhat fluid, and browser vendors of all sizes
added their own elements. First the Internet Engineering Task Force (IETF) and later the
World Wide Web Consortium (W3C) set standards for HTML and its cousin XHTML.