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.
In CSS 2.1, 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;
}
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:
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 or inline box.
The rule below 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).
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 CSS 2.1, 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. A 'close-quote' that would make the depth negative is in error and is ignored (at rendering time): the depth stays at 0 and no quote mark is rendered (although the rest of the 'content' property's value is still inserted).
Note. The 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.
If a quotation is in a different language than the surrounding text, the quote marks of the language of the surrounding text is often used. 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: "“" "”" "‘" "’" }
CSS 2.1 offers basic visual formatting of lists. An element with 'display: list-item' generates a principal box for the element's content and an optional marker box as a visual indication that the element is a list item.
The list properties describe basic visual formatting of lists: they allow style sheets to specify the marker type (image, glyph, or number), and the marker 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.
The background properties apply to the principal box only; an 'outside' marker box is transparent.
| 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.
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'.
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.
The list marker alignment (here, right justified) depends on the user agent.
| 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: | see individual 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" element */
ul > li > ul { list-style: circle outside } /* Any "ul" child
of an "li" child
of a "ul" element */
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.