Beginning HTML ordered lists with numbers other than 1

Yes it is possible and easy! You only have to use the (rare/unknown?) start attribute at your ordered list element (see example below).

<ol start="4">
  <li>list item 1</li>
  <li>list item 2</li>
  <li>list item 3</li>
  <li>list item 4</li>
  <li>list item 5</li>
</ol>

And guess what? It works with negative numbers as well!