CSS Level 3 target-counter() and target-counters() Functions

The CSS Level 3 functions target-counter and target-counters can be used as values for the content property to retrieve counter values and display information obtained from a target at the end of a link.

The target-counter Function

This function retrieves the value of the innermost counter with a given name.

target-counter ( <fragment> , <counter-name> [ , <counter-style> ] ? )

fragment: The URI fragment pointing to the ID of the target element.
counter-name: The name of the counter. This argument is required.
counter-style: This optional argument can be used to format the result.

Example:

HTML:

<nav>
  <ol>
    <li class="frontmatter"><a href="#pref_01">Preface</a></li>
    <li class="frontmatter"><a href="#intr_01">Introduction</a></li>
    <li class="bodymatter"><a href="#chap_01">Chapter One</a></li>
  </ol>
</nav>

CSS:

.frontmatter a::after { content: leader('.') target-counter(attr(href), page, lower-roman) }
.bodymatter a::after { content: leader('.') target-counter(attr(href), page, decimal) }

Result:

The target-counters Function

This function fetches the value of all counters of a given name from the end of a link and formats them by inserting a given string between the value of each nested counter.

target-counter ( <fragment> , <counter-name> , <delimiter> [ , <counter-style> ] ? )

fragment: The URI fragment pointing to the ID of the target element.
counter-name: The name of the counter. This argument is required.
delimiter: The string to be inserted between the value of each nested counter. This argument is required.
counter-style: This optional argument can be used to format the result.