HTML and CSS Reference
Versions of HTML
The first public version of HTML.
Added interactive elements including Web forms.
A proposed replacement for HTML 2.0 that was never widely
Included additional support for Web tables and expanded the
options for interactive form elements and a scripting language.
Added support for style sheets to give Web designers greater control
over page layout and appearance, and provided support for multi-
media elements such as audio and video. Current browsers support
almost all of HTML 4.01.
A reformulation of HTML 4.01 in the XML language in order to pro-
vide enforceable standards for HTML content and to allow HTML to
interact with other XML languages.
A minor update to XHTML 1.0 that allows for modularity and simpli-
fies writing extensions to the language.
The follow-up version to XHTML 1.1 designed to fix some of the prob-
lems inherent in HTML 4.01 syntax. Work on this version was discon-
tinued in 2009 due to lack of browser support.
An update to HTML 4.01 that provides support for a variety of new
features including semantic page elements, column layout, form vali-
dation, offline storage, and enhanced multimedia.
A version of HTML 5.0 written under the XML language; unlike
XHTML 2.0, XHTML 5.0 will be backward compatible with XHTML 1.1.
Figure 1-1 summarizes the various versions of HTML that have been developed over
the past 20 years. You may be wondering how on Earth anything can be written with so
many versions of HTML to consider. At the time of this writing, you can write your code
following the standards of HTML 4.01 or XHTML 1.1 and be assured that it will be sup-
ported by all major browsers. Many features of HTML5 are also being rapidly adopted
by the market even as work continues on developing the language. HTML5 is the future,
but the challenges for Web designers today lie in knowing which parts of HTML5 are
supported by which browsers, and in developing strategies for supporting older browsers
even as HTML5 is being implemented.
In this topic you'll use HTML5 code for those features that have already achieved sup-
port among current browsers, but you'll also learn the standards used for HTML 4.01 and
XHTML 1.1 and practice writing code that will support both current and older browsers.
HTML and Style Sheets
HTML marks the different parts of a document, but it does not indicate how document
content should be displayed by browsers. This is a necessary facet of HTML because a
Web page author has no control over what device will actually view his or her docu-
ment. An end user might be using a large-screen television monitor, a mobile phone, or
even a device that renders Web pages in Braille or in aural speech.
For this reason, the exact appearance of each page element is described in a sepa-
rate document known as a style sheet . Each browser has its own internal style sheet
that specifi es the appearance of different HTML elements. For example, content that is
marked as containing the text of an address is rendered by most Web browsers in italic,
while major headings usually appear in large bold-faced fonts.