- From: Elika Etemad via cvs-syncmail <cvsmail@w3.org>
- Date: Wed, 10 Aug 2011 23:44:30 +0000
- To: public-css-commits@w3.org
Update of /sources/public/csswg/css3-values
In directory hutz:/tmp/cvs-serv7425
Modified Files:
Overview.html Overview.src.html
Log Message:
Generic Values Reorganization Part III: Lengths
Also, sync with CSS2.1.
Index: Overview.html
===================================================================
RCS file: /sources/public/csswg/css3-values/Overview.html,v
retrieving revision 1.74
retrieving revision 1.75
diff -u -d -r1.74 -r1.75
--- Overview.html 10 Aug 2011 23:43:22 -0000 1.74
+++ Overview.html 10 Aug 2011 23:44:28 -0000 1.75
@@ -165,12 +165,9 @@
<li><a href="#syntax-and-terminology"><span class=secno>3. </span>Syntax
and terminology</a>
<ul class=toc>
- <li><a href="#numbers-with-unit-identifiers"><span class=secno>3.1.
- </span>Numbers with unit identifiers</a>
-
- <li><a href="#strings"><span class=secno>3.2. </span>Strings</a>
+ <li><a href="#strings"><span class=secno>3.1. </span>Strings</a>
- <li><a href="#functional-notation"><span class=secno>3.3.
+ <li><a href="#functional-notation"><span class=secno>3.2.
[...2509 lines suppressed...]
- <li>vh (unit), <a href="#vh" title="vh
- (unit)"><strong>5.4.2.6.</strong></a>
+ <li>used value, <a href="#used-value" title="used
+ value"><strong>8.3.</strong></a>
- <li>vm (unit), <a href="#vm" title="vm
- (unit)"><strong>5.4.2.7.</strong></a>
+ <li>vh, <a href="#vh-unit" title=vh><strong>6.1.2.</strong></a>
- <li>vw (unit), <a href="#vw" title="vw
- (unit)"><strong>5.4.2.5.</strong></a>
+ <li>vm, <a href="#vm-unit" title=vm><strong>6.1.2.</strong></a>
- <li>x-height, <a href="#ex" title=x-height><strong>5.4.2.2.</strong></a>
- </ul>
- <!--end-index-->
+ <li>vw, <a href="#vw-unit" title=vw><strong>6.1.2.</strong></a>
+ </ul>
+ <!--end-index-->
+ </dl>
Index: Overview.src.html
===================================================================
RCS file: /sources/public/csswg/css3-values/Overview.src.html,v
retrieving revision 1.77
retrieving revision 1.78
diff -u -d -r1.77 -r1.78
--- Overview.src.html 10 Aug 2011 23:43:22 -0000 1.77
+++ Overview.src.html 10 Aug 2011 23:44:28 -0000 1.78
@@ -269,16 +269,6 @@
common syntactic building blocks and terms that are described in this
section.
-<h3>Numbers with unit identifiers</h3>
-
-<p>A <dfn>number with a unit identifier</dfn> is a number immediately followed by a unit identifier.
-
-<div class="example">
-<pre>
-border-left: -1.2em
-</pre>
-</div>
-
<h3>Strings</h3>
<p>A <dfn>string</dfn> is a sequence of characters enclosed by double quotes or single quotes. Double quotes cannot occur inside double quotes, unless escaped (as '\"' or as '\22'). Analogously for single quotes ("\'" or "\27").<!--"-->
@@ -458,201 +448,318 @@
If the value is outside the allowed range, the declaration is invalid
and must be <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
-<h3><length></h3>
-
-<p>Lengths are denoted by <dfn><length></dfn> in the property
-definitions. Lengths refer to horizontal or vertical measurements.
-Lengths are numbers with a unit identifier. After the '0' length, the
-unit identifier is optional.</p>
-
-<p>Some properties allow negative length values, but this may
-complicate the formatting and there may be implementation-specific
-limits. If a negative length value is allowed but cannot be supported,
-it should be converted to the nearest value that can be supported.</p>
-
-<p>There are several types of length units. <dfn>Relative length
-units</dfn> specify a length relative to other lengths,
-while <dfn>absolute length units</dfn> express fixed lengths.
-
-<h4>Absolute length units: cm, mm. in, pt, pc</h4>
-
-<p>Absolute length units are useful when the physical
-properties of the output medium are known. The absolute units are:</p>
-
-<table>
-<tr><th>unit<th>definition
-<tr><td><span class="css">cm</span><td>centimeters
-<tr><td><span class="css">mm</span><td>millimeters
-<tr><td><span class="css">in</span><td>inches; 1 inch is equal to 2.54 centimeters.
-<tr><td><span class="css">pt</span><td>points; 1pt is equal to 1/72 inch.
-<tr><td><span class="css">pc</span><td>picas; 1 pica is equal to 12 points.
-</table>
-
-<div class="example">
+<h2 id="lengths">
+Distance Units: the ''<length>'' type</h2>
-<pre>
-h1 { margin: 0.5in } /* inches */
-h2 { line-height: 3cm } /* centimeters */
-h3 { word-spacing: 4mm } /* millimeters */
-h4 { font-size: 12pt } /* points */
-h4 { font-size: 1pc } /* picas */</pre>
-</div>
+ <p>Lengths refer to distance measurements and are denoted by
+ <dfn id="length-value"><code><length></code></dfn> in the
+ property definitions.
+ A length is a <i>dimension</i>. A zero length may be represented
+ instead as the <code><number></code> ''0''. (In other words,
+ for zero lengths the unit identifier is optional.)</p>
-<p>In cases where the specified length cannot be supported, user agents must
-approximate it in the actual value.</p>
+ A <dfn>dimension</dfn> is a <i>number</i> immediately followed by a
+ unit identifier. It corresponds to the <code>DIMENSION</code> token in the
+ <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">grammar</a>.
+ [[!CSS21]] Like keywords, unit identifiers are case-insensitive within
+ the ASCII range.
+ <p>Properties may restrict the length value to some range.
+ If the value is outside the allowed range, the declaration is invalid
+ and must be <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
-<h4>Relative length units</h4>
+ <p>While some properties allow negative length values, this may
+ complicate the formatting and there may be implementation-specific
+ limits. If a negative length value is allowed but cannot be supported,
+ it must be converted to the nearest value that can be supported.</p>
-<p>Relative units are:</p>
+ <p>In cases where the <a href="#used-value">used</a> length cannot be
+ supported, user agents must approximate it in the
+ <a href="#actual-value">actual</a> value.
-<table>
-<tr><th>unit<th>relative to
-<tr><td><span class="css">em</span><td>the font size of the element (or, to the parent element's font size if set on the <span class="property">'font-size'</span> property)
-<tr><td><span class="css">ex</span><td>the <em>x-height</em> of the element's font
-<tr><td><span class="css">px</span<td>viewing device
-<tr><td><span class="css">rem</span><td>the font size of the root element
-<tr><td><span class="css">vw</span><td>the viewport's width
-<tr><td><span class="css">vh</span><td>the viewport's height
-<tr><td><span class="css">vm</span><td>the viewport's height or width, whichever is smaller of the two
-<tr><td><span class="css">ch</span><td>The width of the "0" (ZERO, U+0030) glyph found in the font for the font size used to render. If the "0" glyph is not found in the font, the average character width may be used. <span class="issue">How is the "average character width" found?</span>
-</table>
+ <p>There are two types of length units: relative and absolute.
+<h3 id="relative-lengths">
+Relative lengths</h3>
-<h5>The 'em' unit</h5>
+ <p><dfn title="relative length">Relative length units</dfn> specify a
+ length relative to another length. Style sheets that use relative
+ units can more easily scale from one output environment to another.
-<p>The <dfn title="em (unit)">em</dfn> unit is equal to the
-computed value of the 'font-size' property of the element on which it
-is used. The exception is when "em" occurs in the value of the
-'font-size' property itself, in which case it refers to the font size
-of the parent element.
+ <p>The relative units are:</p>
+
+ <table class="data">
+ <caption>Informative Summary of Relative Units</caption>
+ <thead>
+ <tr><th>unit<th>relative to
+ </thead>
+ <tbody>
+ <tr><td>''em''
+ <td>font size of the element
+ <tr><td>''ex''
+ <td><i>x-height</i> of the element's font
+ <tr><td>''ch''
+ <td>width of the "0" glyph in the element's font
+ <tr><td>''rem''
+ <td>font size of the root element
+ <tr><td>''vw''
+ <td>viewport's width
+ <tr><td>''vh''
+ <td>viewport's height
+ <tr><td>''vm''
+ <td>minimum of the viewport's height and width
+ </tbody>
+ </table>
-<p>When specified on the 'font-size' property of the root element, the ''em'' units refer to the
-property's <em>initial value</em>.</p>
+ <p>Child elements do not inherit the relative values as specified for
+ their parent; they inherit the <a href="#computed-value">computed values</a>.
+<h4 id="font-relative-lengths">
+Font-relative lengths: the ''em'', ''ex'', ''ch'', ''rem'' units</h4>
-<p>The rule:</p>
+ <p>Aside from ''rem'' (which refers to the font-size of the root element),
+ the font-relative lengths refer to the computed font metrics of the
+ element on which they are used.
+ The exception is when they occur in the value of the 'font-size' property
+ itself, in which case they refer to the font metrics of the parent element
+ (or the font metrics corresponding to the initial values of the 'font'
+ property, if the element has no parent).
-<pre class="example">
-h1 { line-height: 1.2em }
-</pre>
+ <dl>
+ <dt><dfn title="em">em unit</dfn>
+ <dd><p>Equal to the computed value of the 'font-size' property of
+ the element on which it is used.
-<p>means that the line height of <code>h1</code> elements will be 20% greater than the font size of the elements. On the other hand:</p>
+ <div class="example">
+ <p>The rule:</p>
+ <pre>h1 { line-height: 1.2em }</pre>
+ <p>means that the line height of <code>h1</code> elements will be
+ 20% greater than the font size of <code>h1</code> element. On the
+ other hand:
+ <pre>h1 { font-size: 1.2em }</pre>
+ <p>means that the font size of <code>h1</code> elements will be 20%
+ greater than the font size inherited by <code>h1</code> elements.</p>
+ </div>
-<div class="example">
-<pre>
-h1 { font-size: 1.2em }
-</pre>
+ <dt><dfn title="ex">ex unit</dfn>
+ <dd><p>Equal to the font's x-height. The x-height is so called because
+ it is often equal to the height of the lowercase "x". However, an
+ ''ex'' is defined even for fonts that do not contain an "x".
+ <p>The x-height of a font can be found in different ways. Some fonts
+ contain reliable metrics for the x-height. If reliable font metrics
+ are not available, UAs may determine the x-height from the height
+ of a lowercase glyph. One possible heuristic is to look at how far
+ the glyph for the lowercase "o" extends below the baseline, and
+ subtract that value from the top of its bounding box. In the cases
+ where it is impossible or impractical to determine the x-height,
+ a value of 0.5em must be assumed.
-<p>means that the font size of <code>h1</code> elements will be 20%
-greater than the font size inherited by <code>h1</code> elements.</p> </div>
+ <dt><dfn title="ch">ch unit</dfn>
+ <dd><p>Equal to the advance measure of the "0" (ZERO, U+0030) glyph
+ found in the font used to render it.
+ <dt><dfn title="rem">rem unit</dfn>
+ <dd><p>Equal to the computed value of 'font-size' on the root element.
+ <p>When specified on the 'font-size' property of the root element, the
+ ''rem'' units refer to the property's <em>initial value</em>.</p>
+ </dl>
-<div class="example">
-<pre>
-h1 { margin: 0.5em } /* em */
-h1 { margin: 1ex } /* ex */
-p { font-size: 12px } /* px */
-</pre>
-</div>
+<h4 id="viewport-relative-lengths">
+Viewport-relative lengths: the ''vw'', ''vh'', ''vm'' units</h4>
-<h5>The 'ex' unit</h5>
+ <p>The viewport-relative lengths are relative to the size of the initial
+ containing block. When the height or width of the viewport is changed,
+ they are scaled proportionally.
-<p>The <dfn title="x-height|ex (unit)">ex</dfn> unit is defined by the
-font's x-height. The x-height is so called because it is often equal to the
-height of the lowercase "x". However, an ''ex'' is defined even for fonts that
-do not contain an "x". <span class="issue">Should we say that ex is 0.5em if no better value exists?</span></p>
+ <dl>
+ <dt><dfn title="vw">vw unit</dfn>
+ <dd>Equal to 1/100th of the width of the initial containing block.
+ <div class="example">
+ <p>In the example below, if the width of the viewport is 200mm,
+ the font size of <code>h1</code> elements will be
+ 16mm (i.e. (8×200mm)/100).
+ <pre>h1 { font-size: 8vw }</pre>
+ </div>
-<p>When specified on the 'font-size' property of the root element, the ''ex'' units refer to the
-property's <em>initial value</em>.</p>
+ <dt><dfn title="vh">vh unit</dfn>
+ <dd>Equal to 1/100th of the height of the initial containing block.
+ <dt><dfn title="vm">vm unit</dfn>
+ <dd>Equal to the smaller of ''vw'' or ''vh''.
+ <p class=issue>Do we need this now that we have the min() function?
+ </dl>
-<h5>The 'px' unit</h5>
+<h3 id="absolute-lengths">
+Absolute lengths: the ''cm'', ''mm'', ''in'', ''pt'', ''pc'', ''px'' units</h4>
-<p>The pixel unit, <dfn title="pixel unit|px (pixel)">px</dfn> is relative to the resolution of the viewing device.
-For example, the viewing device can be a computer display or a
-printer. Normally, the pixel unit refers to physical pixels of the
-viewing device. However, if the pixel density of the output device is
-very different from that of a typical computer display, the user agent
-should rescale pixel values. It is recommended that the <dfn>reference
-pixel</dfn> be the visual angle of one pixel on a device with a pixel
-density of 96dpi and a distance from the reader of an arm's length.
-For a nominal arm's length of 28 inches, the visual angle is therefore
-about 0.0213 degrees.</p>
-<p>For reading at arm's length, 1px thus corresponds to about 0.26mm
-(1/96 inch). When printed on a laser printer, meant for reading at a little
-less than arm's length (55 cm, 21 inches), 1px is about 0.21mm. On a 300
-dots-per-inch (dpi) printer, that may be rounded up to 3 dots (0.25 mm); on a
-600 dpi printer, it can be rounded to 5 dots.</p>
+ <p>The <dfn>absolute length units</dfn> are fixed in relation to
+ each other and anchored to some physical measurement.
+ They are mainly useful when the output environment is known.
+ The absolute units consist of the physical units (in, cm, mm, pt, pc)
+ and the px unit:
-<p>The two images below illustrate the effect of viewing distance on the size
-of a pixel and the effect of a device's resolution. In the first image, a
-reading distance of 71cm (28 inch) results in a px of 0.26mm, while a
-reading distance of 3.5m (12 feet) requires a px of 1.3mm.</p>
+ <table class="data">
+ <thead>
+ <tr><th>unit<th>definition
+ </thead>
+ <tbody>
+ <tr><td>''cm''
+ <td>centimeters
+ <tr><td>''mm''
+ <td>millimeters
+ <tr><td>''in''
+ <td>inches; 1in is equal to 2.54cm
+ <tr><td>''px''
+ <td>pixels; 1px is equal to 1/96th of 1in
+ <tr><td>''pt''
+ <td>points; 1pt is equal to 1/72nd of 1in
+ <tr><td>''pc''
+ <td>picas; 1pc is equal to 12pt
+ </tbody>
+ </table>
-<div class="figure">
-<p><img src="pixel1" alt="Showing that pixels must become larger if the viewing distance increases">
-</p>
+<pre class="example">
+h1 { margin: 0.5in } /* inches */
+h2 { line-height: 3cm } /* centimeters */
+h3 { word-spacing: 4mm } /* millimeters */
+h4 { font-size: 12pt } /* points */
+h4 { font-size: 1pc } /* picas */
+p { font-size: 12px } /* px */</pre>
</div>
-<p>In the second image, an area of 1px by 1px is covered by a single dot in a
-low-resolution device (a computer screen), while the same area is covered by
-16 dots in a higher resolution device (such as a 400 dpi laser printer).</p>
-
-<div class="figure">
-<p><img src="pixel2"
-alt="Showing that more device pixels (dots) are needed to cover a 1px by 1px area on a high-resolution device than on a low-res one">
-</p>
-</div>
+ <p>For a CSS device, these dimensions are either anchored (i) by
+ relating the physical units to their physical measurements, or
+ (ii) by relating the pixel unit to the <i>reference pixel</i>.
+ For print media and similar high-resolution devices, the anchor unit
+ should be one of the standard physical units (inches, centimeters, etc).
+ For lower-resolution devices, and devices with unusual viewing distances,
+ it is recommended instead that the anchor unit be the pixel unit. For
+ such devices it is recommended that the pixel unit refer to the whole
+ number of device pixels that best approximates the reference pixel.
+
+ <p class="note">Note that if the anchor unit is the pixel unit,
+ the physical units might not match their physical measurements.
+ Alternatively if the anchor unit is a physical unit, the pixel
+ unit might not map to a whole number of device pixels.</p>
+
+ <p class="note">Note that this definition of the pixel unit and
+ the physical units differs from previous versions of CSS. In
+ particular, in previous versions of CSS the pixel unit and the
+ physical units were not related by a fixed ratio: the physical
+ units were always tied to their physical measurements while the
+ pixel unit would vary to most closely match the reference pixel.
+ (This change was made because too much existing content relies
+ on the assumption of 96dpi, and breaking that assumption breaks
+ the content.)
-<h5>The 'rem' unit</h5>
+ <p>The <dfn>reference pixel</dfn> is the
+ visual angle of one pixel on a device with a pixel density of 96dpi
+ and a distance from the reader of an arm's length. For a nominal arm's
+ length of 28 inches, the visual angle is therefore about 0.0213
+ degrees. For reading at arm's length, 1px thus corresponds to about
+ 0.26 mm (1/96 inch).
+
+ <p>The image below illustrates the effect of viewing distance on
+ the size of a reference pixel: a reading distance of 71 cm
+ (28 inches) results in a reference pixel of 0.26 mm,
+ while a reading distance of 3.5 m (12 feet) results in
+ a reference pixel of 1.3 mm.
-<p>The <dfn title="root em|rem (unit)">rem</dfn> unit ("root em") is
-relative to the computed value of 'font-size' on the root element.
+ <div class="figure">
+ <p><img src="pixel1.png"
+ alt="This diagram illustrates how the definition of a pixel
+ depends on the users distance from the viewing surface
+ (paper or screen).
+ The image depicts the user looking at two planes, one
+ 28 inches (71 cm) from the user, the second 140 inches
+ (3.5 m) from the user. An expanding cone is projected
+ from the user's eye onto each plane. Where the cone
+ strikes the first plane, the projected pixel is 0.26 mm
+ high. Where the cone strikes the second plane, the
+ projected pixel is 1.4 mm high.">
+ <p class="caption">Showing that pixels must become larger if the
+ viewing distance increases
+ </div>
-<p>When specified on the 'font-size' property of the root element, the
-''rem'' units refer to the property's <em>initial value</em>.</p>
+ <p>This second image illustrates the effect of a device's resolution
+ on the pixel unit: an area of 1px by 1px is covered by a single dot
+ in a low-resolution device (e.g. a typical computer display), while
+ the same area is covered by 16 dots in a higher resolution device
+ (such as a printer).
-<h5>The 'vw' unit</h5>
+ <div class="figure">
+ <p><img src="pixel2.png"
+ alt='This diagram illustrates the relationship between the
+ reference pixel and device pixels (called "dots" below).
+ The image depicts a high resolution (large dot density)
+ laser printer output on the left and a low resolution
+ monitor screen on the right. For the laser printer, one
+ square reference pixel is implemented by 16 dots. For
+ the monitor screen, one square reference pixel is
+ implemented by a single dot.'>
+ <p class="caption">Showing that more device pixels (dots) are needed to
+ cover a 1px by 1px area on a high-resolution device than on a low-res one
+ </div>
-<p>The <dfn title="vw (unit)">vw</dfn> unit is relative to
-the viewport's width. The viewport's width is equal to 100
-'vw' units.
+<h2 id="other-dimensions">
+Other Units</h2>
-<div class="example">
-<p style="display:none">Example:
-<pre>
-h1 { font-size: 8vw }
-</pre>
-</div>
+<h3 id="angles">
+<angle>: ''deg'', ''grad'', ''rad'', ''turn''</h3>
-<p>If the width of the viewport is 200mm, the font size of <code
-class="html">h1</code> elements will be 16mm ((8×200)/100). When
-the width of the viewport is changed (for example, when the browser
-window is enlarged), lengths specified in the 'vw' unit are scaled
-proportionally.
+ <p>Angle values are <i>dimensions</i> denoted by
+ <dfn id="angle-value"><angle></dfn>.
+ The angle unit identifiers are:
+ <dl>
+ <dt><dfn title="deg">deg</dfn>
+ <dd>Degrees. There are 360 degrees in a full circle.
+ <dt><dfn title="grad">grad</dfn>
+ <dd>Gradians. There are 400 gradians in a full circle.
+ <dt><dfn title="rad">rad</dfn>
+ <dd>Radians. There are 2π radians in a full circle.
+ <span class="issue">Who is going to use this anyway?</span>
+ <dt><dfn title="turn">turn</dfn>
+ <dd>Turns. There is 1 turn in a full circle.
+ </dl>
-<h5>The 'vh' unit</h5>
+ <p>For example, a right angle is '90deg' or '100grad' or '0.25turn' or
+ approximately '1.570796326794897rad'.</p>
-<p>The <dfn title="vh (unit)">vh</dfn> unit is relative to
-the viewport's height. The viewport's height is equal to 100
-'vh' units. When the height of the viewport is changed (for example,
-when the browser window is enlarged), lengths specified in the 'vh'
-unit are scaled proportionally.
+<h3 id="time">
+<time>: ''s'', ''ms''</h3>
+ <p>Time values are <i>dimensions</i> denoted by
+ <dfn id="time-value"><time></dfn>.
+ The time unit identifiers are:
-<h5>The 'vm' unit</h5>
+ <dl>
+ <dt><dfn title="s">s</dfn>
+ <dd>Seconds.
+ <dt><dfn title="ms">ms</dfn>
+ <dd>Milliseconds. There are 1000 milliseconds in a second.
+ </dl>
-<p class=issue>Do we need this now that we have the min() function?
+ <p>Properties may restrict the time value to some range.
+ If the value is outside the allowed range, the declaration is invalid
+ and must be <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
-<p>The <dfn title="vm (unit)">vm</dfn> unit is relative to
-the viewport's height or width, whichever of the two is smaller.
-The minimum of the viewport's width/height is equivalent to 100 ''vm''
-units. When the height or width of the viewport is changed, lengths
-specified in the 'vm' unit are scaled proportionally.
+<h3><frequency>: ''Hz'', ''kHz''</h3>
+
+ <p>Frequency values are <i>dimensions</i> denoted by
+ <dfn id="frequency-value"><frequency></dfn>.
+ The frequency unit identifiers are:</p>
+ <dl>
+ <dt><dfn title="Hz">Hz</dfn>
+ <dd>Hertz. It represents the number of occurrences per second.
+ <dt><dfn title="kHz">kHz</dfn>
+ <dd>KiloHertz. A kiloHertz is 1000 Hertz.
+ </ul>
+
+ <p>For example, when representing sound pitches, 200Hz (or 200hz)
+ is a bass sound, and 6kHz (or 6khz) is a treble sound.</p>
<h4>The 'calc', 'min' and 'max' functions</h4>
@@ -785,69 +892,6 @@
</div>
-
-
-<h3><angle></h3>
-
-<p>Angle values (denoted by <dfn
-title="<angle>::definition of"><angle></dfn> in the text) are
-used with aural cascading style sheets.</p>
-
-<p>Their format is a <span class="index"><number></span>
-immediately followed by an angle unit identifier.</p>
-
-<p>Angle unit identifiers are:</p>
-<ul>
- <li><dfn title="deg (degrees)">deg</dfn>: degrees</li>
- <li><dfn title="grad (grads)">grad</dfn>: grads</li>
- <li><dfn title="rad (radians)">rad</dfn>: radians</li>
- <li><dfn title="turn">turn</dfn>: turns</li>
-</ul>
-
-<p>Angle values should be normalized to the range
-0-360deg by the user agent. For example, -10deg and 350deg are equivalent.</p>
-
-<p>For example, a right angle is '90deg' or '100grad' or
-'1.570796326794897rad'.</p>
-
-
-
-<h3><time></h3>
-
-<p>Time values are denoted by <dfn title="<time>::definition of"><time></dfn> in the text. Their format is a <span class="index"><number></span> immediately
-followed by a time unit identifier.</p>
-
-<p>Time unit identifiers are:</p>
-
-<ul>
- <li><dfn title="ms (milliseconds)">ms</dfn>: milliseconds</li>
- <li><dfn title="s (seconds)">s</dfn>: seconds</li>
-</ul>
-
-<p>Time values are always positive.
-
-
-<h3><frequency></h3>
-
-<p>Frequency values (denoted by <dfn title="<frequency>::definition of"><frequency></dfn> in the text) are used with aural cascading style sheets.</p>
-
-<p>Their format is a <span class="index"><number></span> immediately
-followed by a frequency unit identifier.</p>
-
-<p>Frequency unit identifiers are:</p>
-<ul>
- <li><dfn title="Hz (Hertz)">Hz:</dfn> Hertz</li>
- <li><dfn title="kHz (kilohertz)">kHz:</dfn> kilohertz</li>
-</ul>
-
-<p>For example, 200Hz (or 200hz) is a bass sound, and 6kHz (or 6khz) is a
-treble sound.</p>
-
-<p>Frequency values are always positive.
-
-
-
-
<h3><attr></h3>
<p class=issue>Describe the feature fully here, not just a delta from CSS 21.
Received on Wednesday, 10 August 2011 23:44:32 UTC