Clean cache for specific domain within Firefox

  1. Select the Firefox Menu button.
  2. (Within Firefox 57 or newer, select Library)
  3. Select the History icon.
  4. Scroll to the bottom and select Show All History.
  5. Search for the site using the Search History field in the upper-right corner.
  6. Within the results, right-click the appropriate page and select Forget About This Site.