About Character Formatting in HTML...
= Index DOT Html by Brian Wilson [bloo@blooberry.com] =

Justification for Character Formatting

The main intent of SGML (and the derivative HTML language) is to be a device independent language for describing the content of documents. To accomplish this, it tries to divorce presentation rules from textual content. Whereas most HTML elements are not intended to give direct control to the author over how the final layout will look, many newer Character Formatting tags now give the author this control.

Character Formatting (which should be rendered distinctly from non-formatted text) allows the author in-line control over changes to content, whereas the other formatting mechanism, Block Formatting, defines content into distinct sections from surrounding text. A visual browser will usually render Character Formatting changes in place while Block Formatting will render any applicable formatting plus an additional implied line break before and after the content block.

Physical Vs. Virtual Character Formatting Styles

There are two classes of character highlighting styles - Physical [sometimes referred to as "typographical" styles] and Virtual [sometimes referred to as "logical" or "idiomatic" styles.] Each Physical style should be rendered distinctly from other Physical styles, while each Virtual style should be rendered distinctly from other Virtual styles. Many of the Physical styles are the common visual rendering analog for Virtual styles (i.e.: <strong> is usually rendered as boldface: <b>)

Physical Styles

[<big>, <blink>, <b>, <font>, <i>, <ilayer>, <small>, <s, strike>, <strong>, <sub>, <sup>, <tt>, <u>]

Physical styles explicitly describe what the final appearance of the contained text should look like. If the rendering device does not have the capability to produce the indicated Physical style (such as a browser for the visually impaired), this formatting may be lost. Note: The new ILayer tag from Netscape is somewhat of an anomaly here. The nature of its display effects are unlike any of the other physical styles.

Virtual Styles

[<cite>, <code>, <dfn>, <em>, <kbd>, <samp>, <var>]

Virtual styles purposefully do not include any final rendering hints in their definitions. These styles describe instead how the contained text is used in the document (the intended semantic context.)

Which Styles to Use?

The original HTML 2.0 specification contained all the Virtual styles listed above, while including only a few of the listed Physical styles. The many Physical styles now available are more recent and reflect a demand from authors for more explicit rendering control. To improve portability though, it is usually recommended to use Virtual styles rather than Physical in your documents.
Example: Use of the <i> tag to render text in italics will only be effective on those browsers which are capable of displaying italics. Not all browsers are guaranteed to have this ability. It is often better to use logical styles (such as <em>) which allow the browser to display the structure as well as it is able.

A Special Generic Character Style

[<span>]

The introduction of Style Sheets has added two new HTML tags to allow for generic tagging situations where no specific HTML markup would be appropriate. The SPAN tag (and its companion Block Formatting Tag DIV) has no real inherent semantic purpose assigned to its structure - the author can assign Style Sheet properties as needed.

Official References

ftp://ds.internic.net/rfc/rfc1866.txt

RFC 1866: The HTML 2.0 specification (plain text)

http://www.w3.org/pub/WWW/MarkUp/html-spec

The web version of the HTML 2.0 (RFC 1866) specification

http://www.w3.org/pub/WWW/MarkUp/Wilbur/

The HTML 3.2 (Wilbur) proposal
[Includes all HTML 2 character elements and newer formatting elements in common use]

http://www.w3.org/pub/WWW/MarkUp/Cougar/HTML.dtd

The experimental HTML (Cougar) draft
[Demonstrates some of the directions HTML is taking]

http://www.w3.org/pub/WWW/TR/WD-css1.html

Cascading Style Sheets, Level 1 specification draft
[Includes usage of SPAN and DIV]

http://home.netscape.com/assist/net_sites/html_extensions.html

Netscape Extensions to HTML 2.0
[Details Font Size tag usage (this document also used to describe Blink as well)]

http://home.netscape.com/assist/net_sites/html_extensions_3.html

Netscape Extensions to HTML 3.0
[Includes Big, Small, Sub and Sup]

http://www.microsoft.com/workshop/author/newhtml/htmlr020.htm

Internet Explorer 3.0 Tag reference
[Details Font Color and Face usage as well as 2.0, 3.2 and common extensions]

Tutorials

http://www.ncsa.uiuc.edu/General/Internet/WWW/HTMLPrimerP2.html#PV

"A Beginner's Guide to HTML" from NCSA - Logical versus Physical styles

http://www.cs.cmu.edu/afs/cs.cmu.edu/Web/People/tilt/cgh

"Composing Good HTML" - Physical vs. Virtual styles in HTML