Ordered list CSS style includes parent number

Question

We're looking to use CSS to create an ordered list that looks like this:

A.
A.1
A.2
B.
C.
C.1
C.2
C.2.1
C.2.2

How would you include the parent index in the child like this?

Answer 1

You'll need to use CSS counters.

Example (from MDN)

CSS:

ol {
  counter-reset: section;                /* Creates a new instance of the
                                            section counter with each ol
                                            element */
  list-style-type: none;
}
li:before {
  counter-increment: section;            /* Increments only this instance
                                            of the section counter */
  content: counters(section, ".") " ";   /* Adds the value of all instances
                                            of the section counter separated
                                            by a ".". */
}

HTML:

<ol>
 <li>Entry
 <li>Entry
 <li>Entry with subentries
  <ol>
    <li>Entry
    <li>Entry
    <li>Entry
    <li>Entry
  </ol>
 <li>Entry
 <li>Entry
 <li>Entry with subentries
  <ol>
    <li>Entry
    <li>Entry
    <li>Entry
    <li>Entry
  </ol>
</ol>

JSFiddle

Answer 2

You should use CSS counters ^{W3C specs} (as @Zeta) has pointed out, but here is an approach that will handle multiple nesting and latin counters ..

ol{
    list-style: none;
}
ol.roman{
    counter-reset: roman;
}
ol.roman > li:before{
    counter-increment: roman;
    content: counter(roman, upper-latin)".";
    padding-right:5px;
}
ol.roman li ol{
    counter-reset: inner;
}
ol.roman ol li:before{
    counter-increment: inner;
    content: counter(roman, upper-latin)"."counters(inner,'.');
    padding-right:5px;
}

Demo at http://jsfiddle.net/gaby/nZQSF/