Coding lists to appear in HTML, with nested numbering cannot just be done in HTML with nested HTML tags to more than one level.

Suppose you wanted this:

1. TITLE
1.1 Description
2. TITLE
2.1 Description
2.2 Description
2.2.1 Description
3. Title

You need some CSS to achieve that 2.2.1 format. And here it is:

ol { counter-reset: item }
li{ display: block }
li:before { content: counters(item, ".") " "; counter-increment: item }