You already know that paragraphs get a blank line between them by default and you should have realised that you can change that behaviour using CSS. You also know that you can add extra blank lines using br. One final way to emphasise a change in topic is the horizontal rule which is just a line between paragraphs or other objects.
Open links.html and save it as hr.html. Find the h2 heading Things to come. Just before it on a blank line put:
<hr>
Save and view.