HTML..XHTML.The.Definitive.Guide..5th.Ed.1002002 [Electronic resources] نسخه متنی

4.5 Physical Style Tags

Nine physical styles are provided by the current HTML
and XHTML standards: bold, italic, monospaced, underlined,
strikethrough, larger, smaller, superscripted, and subscripted text.
Much to our relief, Netscape 6 has stopped supporting a tenth
physical style, "blinking" text.
All physical style tags require ending tags.

As we discuss physical tags in detail, keep in mind that they convey
an acute styling for the immediate text. For more comprehensive,
document-wide control of text display, use style sheets (see Chapter 8).

4.5.1 The <b> Tag

The
<b> tag is the physical equivalent of the
<strong> content-based style tag, but
without the latter's extended meaning. The
<b> tag explicitly boldfaces a character or
segment of text that is enclosed between it and its corresponding end
tag (</b>). If a boldface font is not
available, the browser may use some other representation, such as
reverse video or underlining.

4.5.2 The <big> Tag

The
<big> tag makes it easy to increase the size
of text. It couldn't be simpler: the browser renders
the text between the <big> tag and its
matching </big> ending tag one font size
larger than the surrounding text. If that text is already at the
largest size, <big> has no effect. [<font>]

Even better, you can nest <big> tags to
enlarge the text. Each <big> tag makes the
text one size larger, up to a limit of size seven, as defined by the
font model.

Be careful with your use of the <big> tag,
though. Because browsers are quite forgiving and try hard to
understand a tag, those that don't support
<big> often interpret it to mean bold.

4.5.3 The <blink> Tag (Obsolete Extension)

Text contained between the
<blink> tag and its end tag
</blink> does just that: blinks on and off.
Netscape for Macintosh, for example, simply and reiteratively
reverses the background and foreground colors for the
<blink>-enclosed text. Neither the HTML nor
the XHTML standard includes <blink>; it was
supported as an extension only by Netscape Navigator versions before
Version 6.

We cannot effectively reproduce the animated effect in these static
pages, but it is easy to imagine and best left to the imagination,
too. Blinking
text has two primary effects: it gets your reader's
attention and then promptly annoys them to no end. Forget about
blinking text.

4.5.4 The <i> Tag

The
<i> tag is like the
<em> content-based style tag. It and its
necessary end tag (</i>) tell the browser to
render the enclosed text in an italic or oblique typeface. If the
typeface is not available to the browser, highlighting, reverse
video, or underlining might be used.

4.5.5 The <s> Tag (Deprecated)

The <s> tag
is an abbreviated form of the <strike> tag
supported by both Internet Explorer and Netscape. It is now a
deprecated tag in HTML 4 and XHTML, meaning don't
use it; it will eventually go away.

4.5.6 The <small> Tag

The
<small> tag works just like its
<big> counterpart (see Section 4.5.2), except it decreases the size of text instead
of increasing it. If the enclosed text is already at the smallest
size supported by the font model, <small>
has no effect.

As with <big>, you can nest
<small> tags to sequentially shrink text.
Each <small> tag makes the text one size
smaller than the containing <small> tag, to
a limit of size 1.

4.5.7 The <strike> Tag (Deprecated)

The popular browsers put a line through ("strike
through") text that appears inside the
<strike> tag and its
</strike> end tag. Presumably, it is an
editing markup that tells the reader to ignore the text passage,
reminiscent of the days before typewriter correction tape.
You'll rarely, if ever, see the tag in use today: it
is deprecated in HTML 4 and XHTML, just one step away from complete
elimination from the standard.

4.5.8 The <sub> Tag

The text contained
between the _{tag and its} end tag gets displayed half a
character's height lower, but in the same font and
size as the current text flow. Both <sub>
and its <sup> counterpart are useful for
math equations and in scientific notation, as well as with chemical
formulæ.

4.5.9 The <sup> Tag

The ^{tag and its} end tag superscripts the enclosed
text; it gets displayed half a character's height
higher, but in the same font and size as the current text flow. This
tag is useful for adding footnotes to your documents, along with
exponential values in equations. In combination with the
<a> tag, you can create nice, hyperlinked
footnotes:

The larval quat 
weevil<a href="#note74"><sup><small>74</small></sup></a> is a

This example assumes that footnotesl
contains all your footnotes, appropriately delimited as named
document fragments.

4.5.10 The <tt> Tag

Like the
<code> and <kbd>
tags, the <tt> tag and its necessary
</tt> end tag direct the browser to display
the enclosed text in a monospaced typeface. For those browsers that
already use a monospaced typeface, this tag may make no discernible
change in the presentation of the text.

4.5.11 The <u> Tag (Deprecated)

This
tag tells the browser to
underline the text contained between the <u>
and the corresponding </u> tag. The
underlining technique is simplistic, drawing the line under spaces
and punctuation as well as the text. This tag is deprecated in HTML 4
and XHTML, but the popular browsers support it.

The same display effects for the <u> tag are
better achieved by using style sheets, covered in Chapter 8.

4.5.12 The dir and lang Attributes

The dir attribute lets you advise the browser
which direction the text within the physical tag should be displayed
in, and lang lets you specify the language used
within the tag. [Section 3.6.1.1] [Section 3.6.1.2]

4.5.13 The class, style, id, and title Attributes

Although each
physical tag has a defined style, you can override that style by
defining your own look for each tag. This new look can be applied to
the physical tags using either the style or
class attributes. [Section 8.1.1]
[Section 8.3]

You also may assign a unique id to the physical style tag, as well as
a less rigorous title, using the respective attribute and
accompanying quote-enclosed string value. [Section 4.1.1.4] [Section 4.1.1.4]

4.5.14 Event Attributes

As with content-based style tags,
user-initiated mouse and keyboard events can happen in and around a
physical style tag's contents. Many of these events
are recognized by the browser if it conforms to current standards,
and, with the respective "on"
attribute and value, you may react to the event by displaying a user
dialog box or activating some multimedia event. [Section 12.3.3]

4.5.15 Summary of Physical Style Tags

The various graphical browsers render text inside the
physical style tags in a similar fashion.
Table 4-2 summarizes these
browsers' display styles for the native tags.
Style-sheet definitions may override these native display
styles.

The following HTML source example illustrates some of the various
physical tags as rendered by Netscape (see Figure 4-12):

Explicitly <b>boldfaced</b>, <i>italicized</i>, or
<tt>teletype-style</tt> text should be used 
<big><big>sparingly</big></big>.
Otherwise, drink <strike>lots</strike> 1x10<sup>6</sup>
drops of H<sub><small><small>2</small></small></sub>O. 

Figure 4-12. Use physical text tags with caution

4.5.16 Allowed Content

Any physical style tag may contain any item allowed in text,
including conventional text, anchors, images, and line breaks. You
can also combine physical style tags with other content-based tags.

4.5.17 Allowed Usage

Any physical style tag may be used anywhere an item allowed in text
can be used. In general, this means anywhere within a document except
in the <title>,
<listing>, and
<xmp> tags. You can use a physical style tag
in a heading, but the browser will probably override and ignore its
effect in lieu of the heading tag.

4.5.18 Combining Physical Styles

You will probably have better luck
combining physical tags than you might have combining content-based
tags to achieve multiple effects. For instance, Netscape renders the
following in bold and italic typeface:

<b><i>Thar she blows!</i></b>

In practice, other browsers may elect to ignore such nesting. The
HTML 4 standard does require the browser to "do its
best" to support every possible combination of
styles, but it does not define how the browser should handle such
combinations. Although most browsers make a good attempt at doing so,
do not assume that all combinations will be available to you.