4.5.5 The ol element

Flow content.
If the element's children include at least one li element: Palpable content.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Zero or more li elements.
Content attributes:
Global attributes
DOM interface:
interface HTMLOListElement : HTMLElement {
           attribute boolean reversed;
           attribute long start;
           attribute DOMString type;

The ol element represents a list of items, where the items have been intentionally ordered, such that changing the order would change the meaning of the document.

The items of the list are the li element child nodes of the ol element, in tree order.

The reversed attribute is a boolean attribute. If present, it indicates that the list is a descending list (..., 3, 2, 1). If the attribute is omitted, the list is an ascending list (1, 2, 3, ...).

The start attribute, if present, must be a valid integer giving the ordinal value of the first list item.

If the start attribute is present, user agents must parse it as an integer, in order to determine the attribute's value. The default value, used if the attribute is missing or if the value cannot be converted to a number according to the referenced algorithm, is 1 if the element has no reversed attribute, and is the number of child li elements otherwise.

The first item in the list has the ordinal value given by the ol element's start attribute, unless that li element has a value attribute with a value that can be successfully parsed, in which case it has the ordinal value given by that value attribute.

Each subsequent item in the list has the ordinal value given by its value attribute, if it has one, or, if it doesn't, the ordinal value of the previous item, plus one if the reversed is absent, or minus one if it is present.

The type attribute can be used to specify the kind of marker to use in the list, in the cases where that matters (e.g. because items are to be referenced by their number/letter). The attribute, if specified, must have a value that is a case-sensitive match for one of the characters given in the first cell of one of the rows of the following table. The type attribute represents the state given in the cell in the second column of the row whose first cell matches the attribute's value; if none of the cells match, or if the attribute is omitted, then the attribute represents the decimal state.

Keyword State Description Examples for values 1-3 and 3999-4001
1 (U+0031) decimal Decimal numbers 1. 2. 3. ... 3999. 4000. 4001. ...
a (U+0061) lower-alpha Lowercase latin alphabet a. b. c. ... ewu. ewv. eww. ...
A (U+0041) upper-alpha Uppercase latin alphabet A. B. C. ... EWU. EWV. EWW. ...
i (U+0069) lower-roman Lowercase roman numerals i. ii. iii. ... mmmcmxcix. i̅v̅. i̅v̅i. ...
I (U+0049) upper-roman Uppercase roman numerals I. II. III. ... MMMCMXCIX. I̅V̅. I̅V̅I. ...

User agents should render the items of the list in a manner consistent with the state of the type attribute of the ol element. Numbers less than or equal to zero should always use the decimal system regardless of the type attribute.

For CSS user agents, a mapping for this attribute to the 'list-style-type' CSS property is given in the rendering section (the mapping is straightforward: the states above have the same names as their corresponding CSS values).

The reversed, start, and type IDL attributes must reflect the respective content attributes of the same name. The start IDL attribute has the same default as its content attribute.

The following markup shows a list where the order matters, and where the ol element is therefore appropriate. Compare this list to the equivalent list in the ul section to see an example of the same items using the ul element.

<p>I have lived in the following countries (given in the order of when
I first lived there):</p>
 <li>United Kingdom
 <li>United States

Note how changing the order of the list changes the meaning of the document. In the following example, changing the relative order of the first two items has changed the birthplace of the author:

<p>I have lived in the following countries (given in the order of when
I first lived there):</p>
 <li>United Kingdom
 <li>United States