numbering-headings.html

<!doctype html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
        <title>Numbering headings</title>
        <style>
            /* Switch numbering on by adding class "countheads" to h1 */
            /* Prevent numbering for a single heading via class "nocount" */
        
            body {
                counter-reset: h2counter;
            }
            h1 {
                counter-reset: h2counter;
            }
    
            .countheads ~ h2:before {
                content: counter(h2counter) ".\0000a0\0000a0";
                counter-increment: h2counter;
            }
            h2.nocount:before {
                content: none;
                counter-increment: none;
            }
            h2 {
                counter-reset: h3counter;
            }
    
            .countheads ~ h3:before {
                content: counter(h2counter) "." counter(h3counter) ".\0000a0\0000a0";
                counter-increment: h3counter;
            }
            h3.nocount:before {
                content: none;
                counter-increment: none;
            }
        </style>
    </head>
    <body>
        <h1 class="countheads">Numbering headings</h1>

        <h2>About</h2>
        <ul>
            <li>Companion blog post: “<a href="http://www.2ality.com/2012/01/numbering-headings.html">Automatically numbering headings via CSS</a>”</li>
            <li>Project <a href="https://github.com/rauschma/html_demos">html_demos</a> on GitHub</li>
        </ul>
        
        <h2>Demonstration</h2>
        <h3>Subheading</h3>
        <h3>One more subheading</h3>
    </body>
</html>