10 Lists
Contents
10.1 Introduction to lists
HTML offers authors several mechanisms for specifying lists of information. All lists must contain one or more list elements. Lists may contain:Unordered information.
| Ordered information.
| Definitions.
| |
The previous list, for example, is an unordered list, created with the UL element:
<UL> <LI>Unordered information. <LI>Ordered information. <LI>Definitions. </UL>
An ordered list, created using the OL element, should contain information where order should be emphasized, as in a recipe:
- Mix dry ingredients thoroughly.
- Pour in wet ingredients.
- Mix for 10 minutes.
- Bake for one hour at 300 degrees.
Definition lists, created using the DL element, generally consist of a series of term/definition pairs (although definition lists may have other applications). Thus, when advertising a product, one might use a definition list:
- Lower cost
- The new version of this product costs significantly less than the previous one!
- Easier to use
- We've changed the product so that it's much easier to use!
- Safe for kids
- You can leave your kids alone in a room with this product and they won't get hurt (not a guarantee).
defined in HTML as:
<DL> <DT><STRONG>Lower cost</STRONG> <DD>The new version of this product costs significantly less than the previous one! <DT><STRONG>Easier to use</STRONG> <DD>We've changed the product so that it's much easier to use! <DT><STRONG>Safe for kids</STRONG> <DD>You can leave your kids alone in a room with this product and they won't get hurt (not a guarantee). </DL>
Lists may also be nested and different list types may be used together, as in the following example, which is a definition list that contains an unordered list (the ingredients) and an ordered list (the procedure):
- The ingredients:
100 g. flour
| 10 g. sugar
| 1 cup water
| 2 eggs
| salt, pepper
| |
- Mix dry ingredients thoroughly.
- Pour in wet ingredients.
- Mix for 10 minutes.
- Bake for one hour at 300 degrees.
The exact presentation of the three list types depends on the user agent. We discourage authors from using lists purely as a means of indenting text. This is a stylistic issue and is properly handled by style sheets.
10.2 Unordered lists (UL), ordered lists (OL), and list items (LI)
<!ELEMENT UL - - (LI)+ -- unordered list --> <!ATTLIST UL %attrs; -- %coreattrs, %i18n, %events -- > <!ELEMENT OL - - (LI)+ -- ordered list --> <!ATTLIST OL %attrs; -- %coreattrs, %i18n, %events -- >
Start tag: required, End tag: required
Start tag: required, End tag: optional
Attribute definitions
- type = style-information [CI]
- Deprecated. This attribute sets the style of a list item. Currently available values are intended for visual user agents. Possible values are described below (along with case information).
- start = number [CN]
- Deprecated. For OL only. This attribute specifies the starting number of the first item in an ordered list. The default starting number is "1". Note that while the value of this attribute is an integer, the corresponding label may be non-numeric. Thus, when the list item style is upper case latin letters (A, B, C, ...), start=3 means "C". When the style is lower case roman numerals, start=3 means "iii", etc.
- value = number [CN]
- Deprecated. For LI only. This attribute sets the number of the current list item. Note that while the value of this attribute is an integer, the corresponding label may be non-numeric (see the start attribute).
- compact [CI]
- Deprecated. When set, this boolean attribute gives a hint to visual user agents to render the list in a more compact way. The interpretation of this attribute depends on the user agent.
Attributes defined elsewhere
Ordered and unordered lists are rendered in an identical manner except that visual user agents number ordered list items. User agents may present those numbers in a variety of ways. Unordered list items are not numbered.
Both types of lists are made up of sequences of list items defined by the LI element (whose end tag may be omitted).
This example illustrates the basic structure of a list.
<UL> <LI> ... first list item... <LI> ... second list item... ... </UL>
DEPRECATED EXAMPLE:
<UL>
<LI> ... Level one, number one...
<OL>
<LI> ... Level two, number one...
<LI> ... Level two, number two...
<OL start="10">
<LI> ... Level three, number one...
</OL>
<LI> ... Level two, number three...
</OL>
<LI> ... Level one, number two...
</UL>
Details about number order. In ordered lists, it is not possible to continue list numbering automatically from a previous list or to hide numbering of some list items. However, authors can reset the number of a list item by setting its value attribute. Numbering continues from the new value for subsequent list items. For example:
<ol> <li value="30"> makes this list item number 30. <li value="40"> makes this list item number 40. <li> makes this list item number 41. </ol>
10.3 Definition lists: the DL, DT, and DD elements
<!-- definition lists - DT for term, DD for its definition --> <!ELEMENT DL - - (DT|DD)+ -- definition list --> <!ATTLIST DL %attrs; -- %coreattrs, %i18n, %events -- >
Start tag: required, End tag: required
<!ELEMENT DT - O (%inline;)* -- definition term --> <!ELEMENT DD - O (%flow;)* -- definition description --> <!ATTLIST (DT|DD) %attrs; -- %coreattrs, %i18n, %events -- >
Start tag: required, End tag: optional
Attributes defined elsewhere
Definition lists vary only slightly from other types of lists in that list items consist of two parts: a term and a description. The term is given by the DT element and is restricted to inline content. The description is given with a DD element that contains block-level content.
Here is an example:
<DL>
<DT>Dweeb
<DD>young excitable person who may mature
into a <EM>Nerd</EM> or <EM>Geek</EM>
<DT>Cracker
<DD>hacker on the Internet
<DT>Nerd
<DD>male so into the Net that he forgets
his wife's birthday
</DL>
Here is an example with multiple terms and descriptions:
<DL>
<DT>Center
<DT>Centre
<DD> A point equidistant from all points
on the surface of a sphere.
<DD> In some field sports, the player who
holds the middle position on the field, court,
or forward line.
</DL>
Another application of DL, for example, is for marking up dialogues, with each DT naming a speaker, and each DD containing his or her words.
10.3.1 Visual rendering of lists
Note.The following is an informative description of the behavior of some current visual user agents when formatting lists. Style sheets allow better control of list formatting (e.g., for numbering, language-dependent conventions, indenting, etc.).
Visual user agents generally indent nested lists with respect to the current level of nesting.
For both OL and UL, the type attribute specifies rendering options for visual user agents.
For the UL element, possible values for the type attribute are disc, square, and circle. The default value depends on the level of nesting of the current list. These values are case-insensitive.
How each value is presented depends on the user agent. User agents should attempt to present a "disc" as a small filled-in circle, a "circle" as a small circle outline, and a "square" as a small square outline.
A graphical user agent might render this as:
for the value "disc"
for the value "circle"
for the value "square"
For the OL element, possible values for the type attribute are summarized in the table below (the are case-sensitive):
| Type | Numbering style | |
|---|---|---|
| 1 | arabic numbers | 1, 2, 3, ... |
| a | lower alpha | a, b, c, ... |
| A | upper alpha | A, B, C, ... |
| i | lower roman | i, ii, iii, ... |
| I | upper roman | I, II, III, ... |
Note that the type attribute is deprecated and list styles should be handled through style sheets.
For example, using CSS, one may specify that the style of numbers for list elements in a numbered list should be lower case roman numerals. In the excerpt below, every OL element belonging to the class "withroman" will have roman numerals in front of its list items.
<STYLE type="text/css">
OL.withroman { list-style-type: lower-roman }
</STYLE>
<BODY>
<OL class="withroman">
<LI> Step one ...
<LI> Step two ...
</OL>
</BODY>
The rendering of a definition list also depends on the user agent. The example:
<DL>
<DT>Dweeb
<DD>young excitable person who may mature
into a <EM>Nerd</EM> or <EM>Geek</EM>
<DT>Cracker
<DD>hacker on the Internet
<DT>Nerd
<DD>male so into the Net that he forgets
his wife's birthday
</DL>
might be rendered as follows:
Dweeb
young excitable person who may mature into a Nerd or Geek
Cracker
hacker on the Internet
Nerd
male so into the Net that he forgets his wife's birthday
10.4 The DIR and MENU elements
DIR and MENU are deprecated.
See the Transitional DTD for the formal definition.
Attributes defined elsewhere
The DIR element was designed to be used for creating multicolumn directory lists. The MENU element was designed to be used for single column menu lists. Both elements have the same structure as UL, just different rendering. In practice, a user agent will render a DIR or MENU list exactly as a UL list.
We strongly recommend using UL instead of these elements.
