Contents
In some cases, authors may want user agents to render content that does not come from the document tree. One familiar example of this is a numbered list; the author does not want to list the numbers explicitly, he or she wants the user agent to generate them automatically. Similarly, authors may want the user agent to insert the word "Figure" before the caption of a figure, or "Chapter 7" before the seventh chapter title. For audio or braille in particular, user agents should be able to insert these strings.
In CSS2, content may be generated by several mechanisms:
Below we describe the mechanisms associated with the 'content' property.
Authors specify the style and location of generated content with the :before and :after pseudo-elements. As their names indicate, the :before and :after pseudo-elements specify the location of content before and after an element's document tree content. The 'content' property, in conjunction with these pseudo-elements, specifies what is inserted.
For example, the following rule inserts the string "Note: " before the content of every P element whose "class" attribute has the value "note":
P.note:before { content: "Note: " }
The formatting objects (e.g., boxes) generated by an element include generated content. So, for example, changing the above style sheet to:
P.note:before { content: "Note: " }
P.note { border: solid green }
would cause a solid green border to be rendered around the entire paragraph, including the initial string.
The :before and :after pseudo-elements inherit any inheritable properties from the element in the document tree to which they are attached.
For example, the following rules insert an open quote mark before every Q element. The color of the quote mark will be red, but the font will be the same as the font of the rest of the Q element:
Q:before {
content: open-quote;
color: red
}
In a :before or :after pseudo-element declaration, non-inherited properties take their initial values.
So, for example, because the initial value of the 'display' property is 'inline', the quote in the previous example is inserted as an inline box (i.e., on the same line as the element's initial text content). The next example explicitly sets the 'display' property to 'block', so that the inserted text becomes a block:
BODY:after {
content: "The End";
display: block;
margin-top: 2em;
text-align: center;
}
Note that an audio user agent would speak the words "The End" after rendering the rest of the BODY content.
User agents must ignore the following properties with :before and :after pseudo-elements: 'position', 'float', list properties, and table properties.
The :before and :after pseudo-elements elements allow values of the 'display' property as follows:
Note. Other values may be permitted in future levels of CSS.
This property is used with the :before and :after pseudo-elements to generate content in a document. Values have the following meanings:
The 'display' property controls whether the content is placed in a block, inline, or marker box.
Authors should put 'content' declarations in @media rules when the content is media-sensitive. For instance, literal text may be used for any media group, but images only apply to the visual + bitmap media groups, and sound files only apply to the aural media group.
The following rule causes a sound file to be played at the end of a quotation (see the section on aural style sheets for additional mechanisms):
@media aural {
BLOCKQUOTE:after { content: url("beautiful-music.wav") }
}
The next rule inserts the text of the HTML "alt" attribute before the image. If the image is not displayed, the reader will still see the "alt" text.
IMG:before { content: attr(alt) }
Authors may include newlines in the generated content by writing the "\A" escape sequence in one of the strings after the 'content' property. This inserts a forced line break, similar to the BR element in HTML. See "Strings" and "Characters and case" for more information on the "\A" escape sequence.
H1:before {
display: block;
text-align: center;
content: "chapter\A hoofdstuk\A chapitre"
}
Generated content does not alter the document tree. In particular, it is not fed back to the document language processor (e.g., for reparsing).
Note. In future levels of CSS, the 'content' property may accept additional values, allowing it to vary the style of pieces of the generated content, but in CSS2, all the content of the :before or :after pseudo-element has the same style.
The following cases can occur:
Here is an example of a 'run-in' header with an :after pseudo-element, followed by a paragraph with a :before pseudo-element. All pseudo-elements are inline (the default) in this example. When the style sheet:
H3 { display: run-in }
H3:after { content: ": " }
P:before { content: "... " }
is applied to this source document:
<H3>Centaurs</H3> <P>have hoofs <P>have a tail
The visual formatting will resemble:
Centaurs: ... have hoofs ... have a tail
In CSS2, authors may specify, in a style-sensitive and context-dependent manner, how user agents should render quotation marks. The 'quotes' property specifies pairs of quotation marks for each level of embedded quotation. The 'content' property gives access to those quotation marks and causes them to be inserted before and after a quotation.
This property specifies quotation marks for any number of embedded quotations. Values have the following meanings:
For example, applying the following style sheet:
/* Specify pairs of quotes for two levels in two languages */
Q:lang(en) { quotes: '"' '"' "'" "'" }
Q:lang(no) { quotes: "«" "»" "<" ">" }
/* Insert quotes before and after Q element content */
Q:before { content: open-quote }
Q:after { content: close-quote }
to the following HTML fragment:
<HTML lang="en">
<HEAD>
<TITLE>Quotes</TITLE>
</HEAD>
<BODY>
<P><Q>Quote me!</Q>
</BODY>
</HTML>
would allow a user agent to produce:
"Quote me!"
while this HTML fragment:
<HTML lang="no">
<HEAD>
<TITLE>Quotes</TITLE>
</HEAD>
<BODY>
<P><Q>Trøndere gråter når <Q>Vinsjan på kaia</Q> blir deklamert.</Q>
</BODY>
</HTML>
would produce:
«Trøndere gråter når <Vinsjan på kaia> blir deklamert.»
Note. While the quotation marks specified by 'quotes' in the previous examples are conveniently located on computer keyboards, high quality typesetting would require different ISO 10646 characters. The following informative table lists some of the ISO 10646 quotation mark characters:
| Approximate rendering | ISO 10646 code (hex) | Description |
|---|---|---|
| " | 0022 | QUOTATION MARK [the ASCII double quotation mark] |
| ' | 0027 | APOSTROPHE [the ASCII single quotation mark] |
| < | 2039 | SINGLE LEFT-POINTING ANGLE QUOTATION MARK |
| > | 203A | SINGLE RIGHT-POINTING ANGLE QUOTATION MARK |
| « | 00AB | LEFT-POINTING DOUBLE ANGLE QUOTATION MARK |
| » | 00BB | RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK |
| ` | 2018 | LEFT SINGLE QUOTATION MARK [single high-6] |
| ' | 2019 | RIGHT SINGLE QUOTATION MARK [single high-9] |
| `` | 201C | LEFT DOUBLE QUOTATION MARK [double high-6] |
| '' | 201D | RIGHT DOUBLE QUOTATION MARK [double high-9] |
| ,, | 201E | DOUBLE LOW-9 QUOTATION MARK [double low-9] |
Quotation marks are inserted in appropriate places in a document with the 'open-quote' and 'close-quote' values of the 'content' property. Each occurrence of 'open-quote' or 'close-quote' is replaced by one of the strings from the value of 'quotes', based on the depth of nesting.
'Open-quote' refers to the first of a pair of quotes, 'close-quote' refers to the second. Which pair of quotes is used depends on the nesting level of quotes: the number of occurrences of 'open-quote' in all generated text before the current occurrence, minus the number of occurrences of 'close-quote'. If the depth is 0, the first pair is used, if the depth is 1, the second pair is used, etc. If the depth is greater than the number of pairs, the last pair is repeated.
Note that this quoting depth is independent of the nesting of the source document or the formatting structure.
Some typographic styles require open quotation marks to be repeated before every paragraph of a quote spanning several paragraphs, but only the last paragraph ends with a closing quotation mark. In CSS, this can be achieved by inserting "phantom" closing quotes. The keyword 'no-close-quote' decrements the quoting level, but does not insert a quotation mark.
The following style sheet puts opening quotation marks on every paragraph in a BLOCKQUOTE, and inserts a single closing quote at the end:
BLOCKQUOTE P:before { content: open-quote }
BLOCKQUOTE P:after { content: no-close-quote }
BLOCKQUOTE P.last:after { content: close-quote }
This relies on the last paragraph being marked with a class "last", since there are no selectors that can match the last child of an element.
For symmetry, there is also a 'no-open-quote' keyword, which inserts nothing, but increments the quotation depth by one.
Note. If a quotation is in a different language than the surrounding text, it is customary to quote the text with the quote marks of the language of the surrounding text, not the language of the quotation itself.
For example, French inside English:
The device of the order of the garter is “Honi soit qui mal y pense.”English inside French:
Il disait: « Il faut mettre l'action en ‹ fast forward ›.»
A style sheet like the following will set the 'quotes' property so that 'open-quote' and 'close-quote' will work correctly on all elements. These rules are for documents that contain only English, French, or both. One rule is needed for every additional language. Note the use of the child combinator (">") to set quotes on elements based on the language of the surrounding text:
[LANG|=fr] > * { quotes: "«" "»" "\2039" "\203A" }
[LANG|=en] > * { quotes: "\201C" "\201D" "\2018" "\2019" }
The quotation marks for English are shown here in a form that most people will be able to type. If you can type them directly, they will look like this:
[LANG|=fr] > * { quotes: "«" "»" "‹" "›" }
[LANG|=en] > * { quotes: "“" "”" "‘" "’" }
Automatic numbering in CSS2 is controlled with two properties, 'counter-increment' and 'counter-reset'. The counters defined by these properties are used with the counter() and counters() functions of the the 'content' property.
| Value: | [ <identifier> <integer>? ]+ | none | inherit |
| Initial: | none |
| Applies to: | all elements |
| Inherited: | no |
| Percentages: | N/A |
| Media: | all |
| Value: | [ <identifier> <integer>? ]+ | none | inherit |
| Initial: | none |
| Applies to: | all elements |
| Inherited: | no |
| Percentages: | N/A |
| Media: | all |
The 'counter-increment' property accepts one or more names of counters (identifiers), each one optionally followed by an integer. The integer indicates by how much the counter is incremented for every occurrence of the element. The default increment is 1. Zero and negative integers are allowed.
The 'counter-reset' property also contains a list of one or more names of counters, each one optionally followed by an integer. The integer gives the value that the counter is set to on each occurrence of the element. The default is 0.
If 'counter-increment' refers to a counter that is not in the scope (see below) of any 'counter-reset', the counter is assumed to have been reset to 0 by the root element.
This example shows a way to number chapters and sections with "Chapter 1", "1.1", "1.2", etc.
H1:before {
content: "Chapter " counter(chapter) ". ";
counter-increment: chapter; /* Add 1 to chapter */
counter-reset: section; /* Set section to 0 */
}
H2:before {
content: counter(chapter) "." counter(section) " ";
counter-increment: section;
}
If an element increments/resets a counter and also uses it (in the 'content' property of its :before or :after pseudo-element), the counter is used after being incremented/reset.
If an element both resets and increments a counter, the counter is reset first and then incremented.
The 'counter-reset' property follows the cascading rules. Thus, due to cascading, the following style sheet:
H1 { counter-reset: section -1 }
H1 { counter-reset: imagenum 99 }
will only reset 'imagenum'. To reset both counters, they have to be specified together:
H1 { counter-reset: section -1 imagenum 99 }
Counters are "self-nesting", in the sense that re-using a counter in a child element automatically creates a new instance of the counter. This is important for situations like lists in HTML, where elements can be nested inside themselves to arbitrary depth. It would be impossible to define uniquely named counters for each level.
Thus, the following suffices to number nested list items. The result is very similar to that of setting 'display:list-item' and 'list-style: inside' on the LI element:
OL { counter-reset: item }
LI { display: block }
LI:before { content: counter(item) ". "; counter-increment: item }
The self-nesting is based on the principle that every element that has a 'counter-reset' for a counter X, creates a fresh counter X, the scope of which is the element, its preceding siblings, and all the descendants of the element and its preceding siblings.
In the example above, an OL will create a counter, and all children of the OL will refer to that counter.
If we denote by item[n] the nth instance of the "item" counter, and by "(" and ")" the beginning and end of a scope, then the following HTML fragment will use the indicated counters. (We assume the style sheet as given in the example above).
<OL> <!-- (set item[0] to 0 -->
<LI>item <!-- increment item[0] (= 1) -->
<LI>item <!-- increment item[0] (= 2) -->
<OL> <!-- (set item[1] to 0 -->
<LI>item <!-- increment item[1] (= 1) -->
<LI>item <!-- increment item[1] (= 2) -->
<LI>item <!-- increment item[1] (= 3) -->
<OL> <!-- (set item[2] to 0 -->
<LI>item <!-- increment item[2] (= 1) -->
</OL> <!-- ) -->
<OL> <!-- (set item[3] to 0 -->
<LI> <!-- increment item[3] (= 1) -->
</OL> <!-- ) -->
<LI>item <!-- increment item[1] (= 4) -->
</OL> <!-- ) -->
<LI>item <!-- increment item[0] (= 3) -->
<LI>item <!-- increment item[0] (= 4) -->
</OL> <!-- ) -->
<OL> <!-- (reset item[4] to 0 -->
<LI>item <!-- increment item[4] (= 1) -->
<LI>item <!-- increment item[4] (= 2) -->
</OL> <!-- ) -->
The 'counters()' function generates a string composed of the values of all counters with the same name, separated by a given string.
The following style sheet numbers nested list items as "1", "1.1", "1.1.1", etc.
OL { counter-reset: item }
LI { display: block }
LI:before { content: counters(item, "."); counter-increment: item }
By default, counters are formatted with decimal numbers, but all the styles available for the 'list-style-type' property are also available for counters. The notation is:
counter(name)
for the default style, or:
counter(name, 'list-style-type')
All the styles are allowed, including 'disc', 'circle', 'square', and 'none'.
H1:before { content: counter(chno, upper-latin) ". " }
H2:before { content: counter(section, upper-roman) " - " }
BLOCKQUOTE:after { content: " [" counter(bq, hebrew) "]" }
DIV.note:before { content: counter(notecntr, disc) " " }
P:before { content: counter(p, none) }
An element that is not displayed ('display' set to 'none') cannot increment or reset a counter.
For example, with the following style sheet, H2s with class "secret" do not increment 'count2'.
H2.secret {counter-increment: count2; display: none}
Elements with 'visibility' set to 'hidden', on the other hand, do increment counters.
Most block-level elements in CSS generate one principal block box. In this section, we discuss two CSS mechanisms that cause an element to generate two boxes: one principal block box (for the element's content) and one separate marker box (for decoration such as a bullet, image, or number). The marker box may be positioned inside or outside the principal box. Unlike :before and :after content, the marker box does not affect the position of the principal box, whatever the positioning scheme.
The more general of the two mechanisms is new in CSS2 and is called markers. The more limited mechanism involves the list properties of CSS1. The list properties give authors quick results for many common ordered and unordered list scenarios. However, markers give authors precise control over marker content and position. Markers may be used with counters to create new list styles, to number margin notes, and much more.
For instance, the following example illustrates how markers may be used to add periods after each numbered list item. This HTML program and style sheet:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<HTML>
<HEAD>
<TITLE>Creating a list with markers</TITLE>
<STYLE type="text/css">
LI:before {
display: marker;
content: counter(mycounter, lower-roman) ".";
counter-increment: mycounter;
}
</STYLE>
</HEAD>
<BODY>
<OL>
<LI> This is the first item.
<LI> This is the second item.
<LI> This is the third item.
</OL>
</BODY>
</HTML>
should produce something like this:
i. This is the first item. ii. This is the second item. iii. This is the third item.
With descendant selectors and child selectors, it's possible to specify different marker types depending on the depth of embedded lists.
Markers are created by setting the 'display' property to 'marker' inside a :before or :after pseudo-element. While 'block' and 'inline' :before and :after content is part of the principal box generated by the element, 'marker' content is formatted in an independent marker box, outside the principal box. Marker boxes are formatted as a single line (i.e., one line box), so they are not as flexible as floats. The marker box is only created if the 'content' property for the pseudo-element actually generates content.
Marker boxes have padding and borders, but no margins.
For the :before pseudo-element, the baseline of text in the marker box will be vertically aligned with the baseline of text in the first line of content in the principal box. If the principal box contains no text, the top outer edge of the marker box will be aligned with the top outer edge of the principal box. For the :after pseudo-element, the baseline of text in the marker box will be vertically aligned with the baseline of text in the last line of content in the principal box. If the principal box contains no text, the bottom outer edge of the marker box will be aligned with the bottom outer edge of the principal box.
The height of a marker box is given by the 'line-height' property. The :before (:after) marker box participates in the height calculation of the principal box's first (last) line box. Thus, markers are aligned with the first and last line of an element's content, even though the marker boxes live in distinct line boxes. If no first or last line box exists in a principal box, the marker box establishes its line box alone.
The vertical alignment of a marker box within its line box is specified with the 'vertical-align' property.
If the value of the 'width' property is 'auto', the marker box content width is that of the content, otherwise it is the value of 'width'. For values of 'width' less than the content width, the 'overflow' property specifies overflow behavior. Marker boxes may overlap principal boxes. For values of 'width' greater than the content width, the 'text-align' property determines the horizontal alignment of the content in the marker box.
The 'marker-offset' property specifies the horizontal offset between a marker box and the associated principal box. The distance is measured between their nearest border edges. Note. If a marker flows to the right of a float in a left-to-right formatting context, the principal box will flow down the float's right side, but the marker boxes will appear to the left of the float. Since the principal box left border edge lies to the left of the float (see the description of floats), and marker boxes lie outside the border edge of the principal box, the marker will also lie to the left of the float. Analogous behavior applies for right-to-left formatting when a marker flows to the left of a float.
When the 'display' property has the value 'marker' for content generated by an element with 'display: list-item', a marker box generated for ':before' replaces the normal list item marker.
In the following example, the content is centered within a marker box of a fixed width. This document:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<HTML>
<HEAD>
<TITLE>Content alignment in the marker box</TITLE>
<STYLE type="text/css">
LI:before {
display: marker;
content: "(" counter(counter) ")";
counter-increment: counter;
width: 6em;
text-align: center;
}
</STYLE>
</HEAD>
<BODY>
<OL>
<LI> This is the first item.
<LI> This is the second item.
<LI> This is the third item.
</OL>
</BODY>
</HTML>
should produce something like this:
(1) This is the
first item.
(2) This is the
second item.
(3) This is the
third item.
The next example creates markers before and after list items.
This document:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<HTML>
<HEAD>
<TITLE>Markers before and after list items</TITLE>
<STYLE type="text/css">
@media screen, print {
LI:before {
display: marker;
content: url("smiley.gif");
LI:after {
display: marker;
content: url("sad.gif");
}
}
</STYLE>
</HEAD>
<BODY>
<UL>
<LI>first list item comes first
<LI>second list item comes second
</UL>
</BODY>
</HTML>
should produce something like this (ascii art is used instead of smiley gif images here):
:-) first list item
comes first :-(
:-) second list item
comes second :-(
The next example uses markers to number notes (paragraphs).
The following document:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<HTML>
<HEAD>
<TITLE>Markers to create numbered notes4>/TITLE>
<STYLE type="text/css">
P { margin-left: 12 em; }
@media screen, print {
P.Note:before {
display: marker;
content: url("note.gif")
"Note " counter(note-counter) ":";
counter-increment: note-counter;
text-align: left;
width: 10em;
}
}
</STYLE>
</HEAD>
<BODY>
<P>This is the first paragraph in this document.</P>
<P CLASS="Note">This is a very short document.</P>
<P>This is the end.</P>
</BODY>
</HTML>
should produce something like:
This is the first paragraph
in this document.
Note 1: This is a very short
document.
This is the end.
| Value: | <length> | auto | inherit |
| Initial: | auto |
| Applies to: | elements with 'display: marker' |
| Inherited: | no |
| Percentages: | N/A |
| Media: | visual |
This property specifies the distance between the nearest border edges of a marker box and its associated principal box. The offset may either be a user-specified (<length>) or chosen by the UA ('auto'). Lengths may be negative, but there may be implementation-specific limits.
The following example illustrates how markers may be used to add periods after each numbered list item. This HTML program and style sheet:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE>Marker example 5</TITLE>
<STYLE type="text/css">
P { margin-left: 8em } /* Make space for counters */
LI:before {
display: marker;
marker-offset: 3em;
content: counter(mycounter, lower-roman) ".";
counter-increment: mycounter;
}
</STYLE>
</HEAD>
<BODY>
<P> This is a long preceding paragraph ...
<OL>
<LI> This is the first item.
<LI> This is the second item.
<LI> This is the third item.
</OL>
<P> This is a long following paragraph ...
</BODY>
</HTML>
should produce something like this:
This is a long preceding
paragraph ...
i. This is the first item.
ii. This is the second item.
iii. This is the third item.
This is a long following
paragraph ...
The list properties allow basic visual formatting of lists. As with more general markers, a element with 'display: list-item' generates a principal box for the element's content and an optional marker box. The other list properties allow authors to specify the marker type (image, glyph, or number) and its position with respect to the principal box (outside it or within it before content). They do not allow authors to specify distinct style (colors, fonts, alignment, etc.) for the list marker or adjust its position with respect to the principal box.
Furthermore, when a marker M (created with 'display: marker') is used with a list item created by the list properties, M replaces the standard list item marker.
With the list properties, the background properties apply to the principal box only; an 'outside' marker box is transparent. Markers offer more control over marker box style.
| Value: | disc | circle | square | decimal | decimal-leading-zero | lower-roman | upper-roman | lower-greek | lower-alpha | lower-latin | upper-alpha | upper-latin | hebrew | armenian | georgian | cjk-ideographic | hiragana | katakana | hiragana-iroha | katakana-iroha | none | inherit |
| Initial: | disc |
| Applies to: | elements with 'display: list-item' |
| Inherited: | yes |
| Percentages: | N/A |
| Media: | visual |
This property specifies appearance of the list item marker if 'list-style-image' has the value 'none' or if the image pointed to by the URI cannot be displayed. The value 'none' specifies no marker, otherwise there are three types of marker: glyphs, numbering systems, and alphabetic systems. Note. Numbered lists improve document accessibility by making lists easier to navigate.
Glyphs are specified with disc, circle, and square. Their exact rendering depends on the user agent.
Numbering systems are specified with:
A user agent that does not recognize a numbering system should use 'decimal'.
Note. This document does not specify the exact mechanism of each numbering system (e.g., how roman numerals are calculated). A future W3C Note may provide further clarifications.
Alphabetic systems are specified with:
This specification does not define how alphabetic systems wrap at the end of the alphabet. For instance, after 26 list items, 'lower-latin' rendering is undefined. Therefore, for long lists, we recommend that authors specify true numbers.
For example, the following HTML document:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<HTML>
<HEAD>
<TITLE>Lowercase latin numbering</TITLE>
<STYLE type="text/css">
OL { list-style-type: lower-roman }
</STYLE>
</HEAD>
<BODY>
<OL>
<LI> This is the first item.
<LI> This is the second item.
<LI> This is the third item.
</OL>
</BODY>
</HTML>
might produce something like this:
i This is the first item. ii This is the second item. iii This is the third item.
Note that the list marker alignment (here, right justified) depends on the user agent.
Note. Future versions of CSS may provide more complete mechanisms for international numbering styles.
| Value: | <uri> | none | inherit |
| Initial: | none |
| Applies to: | elements with 'display: list-item' |
| Inherited: | yes |
| Percentages: | N/A |
| Media: | visual |
This property sets the image that will be used as the list item marker. When the image is available, it will replace the marker set with the 'list-style-type' marker.
The following example sets the marker at the beginning of each list item to be the image "ellipse.png".
UL { list-style-image: url("http://png.com/ellipse.png") }
| Value: | inside | outside | inherit |
| Initial: | outside |
| Applies to: | elements with 'display: list-item' |
| Inherited: | yes |
| Percentages: | N/A |
| Media: | visual |
This property specifies the position of the marker box in the principal block box. Values have the following meanings:
For example:
<HTML>
<HEAD>
<TITLE>Comparison of inside/outside position</TITLE>
<STYLE type="text/css">
UL { list-style: outside }
UL.compact { list-style: inside }
</STYLE>
</HEAD>
<BODY>
<UL>
<LI>first list item comes first
<LI>second list item comes second
</UL>
<UL class="compact">
<LI>first list item comes first
<LI>second list item comes second
</UL>
</BODY>
</HTML>
The above example may be formatted as:
In right-to-left text, the markers would have been on the right side of the box.
| Value: | [ <'list-style-type'> || <'list-style-position'> || <'list-style-image'> ] | inherit |
| Initial: | not defined for shorthand properties |
| Applies to: | elements with 'display: list-item' |
| Inherited: | yes |
| Percentages: | N/A |
| Media: | visual |
The 'list-style' property is a shorthand notation for setting the three properties 'list-style-type', 'list-style-image', and 'list-style-position' at the same place in the style sheet.
UL { list-style: upper-roman inside } /* Any UL */
UL > UL { list-style: circle outside } /* Any UL child of a UL */
Although authors may specify 'list-style' information directly on list item elements (e.g., LI in HTML), they should do so with care. The following rules look similar, but the first declares a descendant selector and the second a (more specific) child selector.
OL.alpha LI { list-style: lower-alpha } /* Any LI descendant of an OL */
OL.alpha > LI { list-style: lower-alpha } /* Any LI child of an OL */
Authors who use only the descendant selector may not achieve the results they expect. Consider the following rules:
<HTML>
<HEAD>
<TITLE>WARNING: Unexpected results due to cascade</TITLE>
<STYLE type="text/css">
OL.alpha LI { list-style: lower-alpha }
UL LI { list-style: disc }
</STYLE>
</HEAD>
<BODY>
<OL class="alpha">
<LI>level 1
<UL>
<LI>level 2
</UL>
</OL>
</BODY>
</HTML>
The desired rendering would have level 1 list items with 'lower-alpha' labels and level 2 items with 'disc' labels. However, the cascading order will cause the first style rule (which includes specific class information) to mask the second. The following rules solve the problem by employing a child selector instead:
OL.alpha > LI { list-style: lower-alpha }
UL LI { list-style: disc }
Another solution would be to specify 'list-style' information only on the list type elements:
OL.alpha { list-style: lower-alpha }
UL { list-style: disc }
Inheritance will transfer the 'list-style' values from OL and UL elements to LI elements. This is the recommended way to specify list style information.
A URI value may be combined with any other value, as in:
UL { list-style: url("http://png.com/ellipse.png") disc }
In the example above, the 'disc' will be used when the image is unavailable.
A value of 'none' for the 'list-style' property sets both 'list-style-type' and 'list-style-image' to 'none':
UL { list-style: none }
The result is that no list-item marker is displayed.