http://www.perlmonks.org?node_id=200987


in reply to Formatting differences between preview and display

At first glance, it looks like you are not opening/closing  <p>paragraphs</p> properly. Maybe the style sheet is compensating for that in some sections (such as in the preview page).

update: the problem actually was not opening  <p> . Closing  </p> is more-or-less optional.