12 Generated content, automatic numbering, and lists

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:

• The 'content' property, in conjunction with the :before and :after pseudo-elements.
• The 'cue-before', 'cue-after' aural properties (see the chapter on aural style sheets). When the 'content' property is combined with the aural properties they are rendered in the following order: :before, 'cue-before', ('pause-before'), the element's content, ('pause-after'), 'cue-after', and :after.
• Elements with a value of 'list-item' for the 'display' property.

Below we describe the mechanisms associated with the 'content' property.

12.1 The :before and :after pseudo-elements

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.

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.

Q:before {
  content: open-quote;
  color: red
}

In a :before or :after pseudo-element declaration, non-inherited properties take their initial values.

BODY:after {
    content: "The End";
    display: block;
    margin-top: 2em;
    text-align: center;
}

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:

• If the subject of the selector is a block-level element, allowed values are 'none', 'inline', 'block', and 'marker'. If the value of the 'display' has any other value, the pseudo-element will behave as if the value were 'block'.
• If the subject of the selector is an inline-level element, allowed values are 'none' and 'inline'. If the value of the 'display' has any other value, the pseudo-element will behave as if the value were 'inline'.

12.2 The 'content' property

This property is used with the :before and :after pseudo-elements to generate content in a document. Values have the following meanings:

<string>

Text content (see the section on strings).

<uri>

The value is a URI that designates an external resource. If a user agent cannot support the resource because of the media types it supports, it must ignore the resource. Note. CSS2 offers no mechanism to change the size of the embedded object, or to provide a textual description, like the "alt" or "longdesc" attributes do for images in HTML. This may change in future levels of CSS.

<counter>

Counters may be specified with two different functions: 'counter()' or 'counters()'. The former has two forms: 'counter(name)' or 'counter(name, style)'. The generated text is the value of the named counter at this point in the formatting structure; it is formatted in the indicated style ('decimal' by default). The latter function also has two forms: 'counter(name, string)' or 'counter(name, string, style)'. The generated text is the value of all counters with the given name at this point in the formatting structure, separated by the specified string. The counters are rendered in the indicated style ('decimal' by default). See the section on automatic counters and numbering for more information.

open-quote and close-quote

These values are replaced by the appropriate string from the 'quotes' property.

no-open-quote and no-close-quote

Inserts nothing (the empty string), but increments (decrements) the level of nesting for quotes.

attr(X)

This function returns as a string the value of attribute X for the subject of the selector. The string is not parsed by the CSS processor. If the subject of the selector doesn't have an attribute X, an empty string is returned. The case-sensitivity of attribute names depends on the document language. Note. In CSS2, it is not possible to refer to attribute values for other elements of the selector.

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.

@media aural {
   BLOCKQUOTE:after { content: url("beautiful-music.wav") }
   }

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).

12.3 Interaction of :before and :after with 'compact' and 'run-in' elements

The following cases can occur:

1. A 'run-in' or 'compact' element has a :before pseudo-element of type 'inline': the pseudo-element is taken into account when the size of the element's box is computed (for 'compact') and is rendered inside the same block box as the element.
2. A 'run-in' or 'compact' element has an :after pseudo-element of type 'inline': The rules of the previous point apply.
3. A 'run-in' or 'compact' element has a :before pseudo-element of type 'block': the pseudo-element is formatted as a block above the element, and does not take part in the computation of the element's size (for 'compact').
4. A 'run-in' or 'compact' element has an :after pseudo-element of type 'block': both the element and its :after pseudo-element are formatted as block boxes. The element is not formatted as an inline box in its own :after pseudo-element.
5. The element following a 'run-in' or 'compact' element has a :before of type 'block': the decision how to format the 'run-in'/'compact' element is made with respect to the block box resulting from the :before pseudo-element.
6. The element following a 'run-in' or 'compact' element has an :before of type 'inline': the decision how to format the 'run-in'/'compact' element depends on the 'display' value of the element to which the :before is attached.

H3 { display: run-in }
H3:after { content: ": " }
P:before { content: "... " }

<H3>Centaurs</H3>
<P>have hoofs
<P>have a tail

Centaurs: ... have hoofs
... have a tail

12.4 Quotation marks

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.

12.4.1 Specifying quotes with the 'quotes' property

This property specifies quotation marks for any number of embedded quotations. Values have the following meanings:

none

The 'open-quote' and 'close-quote' values of the 'content' property produce no quotations marks.

[<string> �<string>]+

Values for the 'open-quote' and 'close-quote' values of the 'content' property are taken from this list of pairs of quotation marks (opening and closing). The first (leftmost) pair represents the outermost level of quotation, the second pair the first level of embedding, etc. The user agent must apply the appropriate pair of quotation marks according to the level of embedding.

/* 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 }

<HTML lang="en">
  <HEAD>
  <TITLE>Quotes</TITLE>
  </HEAD>
  <BODY>
    <P><Q>Quote me!</Q>
  </BODY>
</HTML>

"Quote me!"

<HTML lang="no">
  <HEAD>
  <TITLE>Quotes</TITLE>
  </HEAD>
  <BODY>
    <P><Q>Tr�ndere gr�ter n�r <Q>Vinsjan p� kaia</Q> blir deklamert.</Q>
  </BODY>
</HTML>

�Tr�ndere gr�ter n�r <Vinsjan p� kaia> blir deklamert.�

12.4.2 Inserting quotes with the 'content' property

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.

BLOCKQUOTE P:before     { content: open-quote }
BLOCKQUOTE P:after      { content: no-close-quote }
BLOCKQUOTE P.last:after { content: close-quote }

For symmetry, there is also a 'no-open-quote' keyword, which inserts nothing, but increments the quotation depth by one.

[LANG|=fr] > *  { quotes: "�" "�" "\2039" "\203A" }
[LANG|=en] > *  { quotes: "\201C" "\201D" "\2018" "\2019" }

[LANG|=fr] > * { quotes: "�" "�" "‹" "›" }
[LANG|=en] > * { quotes: "“" "”" "‘" "’" }

12.5 Automatic counters and numbering

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.

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.

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 }

12.5.1 Nested counters and scope

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.

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.

<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.

OL { counter-reset: item }
LI { display: block }
LI:before { content: counters(item, "."); counter-increment: item }

12.5.2 Counter styles

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) }

12.5.3 Counters in elements with 'display: none'

An element that is not displayed ('display' set to 'none') cannot increment or reset a counter.

H2.secret {counter-increment: count2; display: none}

Elements with 'visibility' set to 'hidden', on the other hand, do increment counters.

12.6 Markers and lists

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.

<!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>

   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.

12.6.1 Markers: the 'marker-offset' property

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.

<!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>

  (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.

<!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>

  :-) first list item 
      comes first      :-(
  :-) second list item 
      comes second     :-(

The next example uses markers to number notes (paragraphs).

<!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>

            This is the first paragraph 
            in this document.

  Note 1:   This is a very short 
            document.
           
            This is the end.

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.

<!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>

        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 ...

12.6.2 Lists: the 'list-style-type', 'list-style-image', 'list-style-position', and 'list-style' properties

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.

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:

decimal

Decimal numbers, beginning with 1.

decimal-leading-zero

Decimal numbers padded by initial zeros (e.g., 01, 02, 03, ..., 98, 99).

lower-roman

Lowercase roman numerals (i, ii, iii, iv, v, etc.).

upper-roman

Uppercase roman numerals (I, II, III, IV, V, etc.).

hebrew

Traditional Hebrew numbering.

georgian

Traditional Georgian numbering (an, ban, gan, ..., he, tan, in, in-an, ...).

armenian

Traditional Armenian numbering.

cjk-ideographic

Plain ideographic numbers

hiragana

a, i, u, e, o, ka, ki, ...

katakana

A, I, U, E, O, KA, KI, ...

hiragana-iroha

i, ro, ha, ni, ho, he, to, ...

katakana-iroha

I, RO, HA, NI, HO, HE, TO, ...

A user agent that does not recognize a numbering system should use 'decimal'.

Alphabetic systems are specified with:

lower-latin or lower-alpha

Lowercase ascii letters (a, b, c, ... z).

upper-latin or upper-alpha

Uppercase ascii letters (A, B, C, ... Z).

lower-greek

Lowercase classical Greek alpha, beta, gamma, ... (έ, ή, ί, ...)

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.

<!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>

  i This is the first item.
 ii This is the second item.
iii This is the third item.

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.

UL { list-style-image: url("http://png.com/ellipse.png") }

This property specifies the position of the marker box in the principal block box. Values have the following meanings:

outside

The marker box is outside the principal block box. Note. CSS1 did not specify the precise location of the marker box and for reasons of compatibility, CSS2 remains equally ambiguous. For more precise control of marker boxes, please use markers.

inside

The marker box is the first inline box in the principal block box, after which the element's content flows.

<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>

In right-to-left text, the markers would have been on the right side of the box.

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.

UL { list-style: url("http://png.com/ellipse.png") disc }

UL { list-style: none }