title: How href="#" works?
body: <p><a href="https://www.rcsb.org/stats/growth/overall" rel="nofollow noreferrer">https://www.rcsb.org/stats/growth/overall</a></p>
  
  <p>On the above page, the link under "CSV" is shown as <code>https://www.rcsb.org/stats/growth/overall#</code>. When I click it, it will download a CSV file. Could anybody show me how the browser figure out the actual download URL? Thanks.</p>