To delete the cache on a Mac in the Firefox browser, please do the following:

  1. In the main menu of the browser select "History" and below that the submenu-item "Clear Recent History..."
  2. A popup opens. In the drop-down menu, you can define the time range you want to delete the cache. You have the following options: last hour, last two hours, last four hours, today or Everything.
  3. To delete all cache data, select "Everything" from the drop-down menu.
  4. Afterwards, click on the arrow next to "Details" to show the different possibilities for which data should be deleted. If you want to delete only the cache, then check only the checkbox next to "Cache".
  5. With a click on the button "Clear now" you delete the cache.
  6. Reload the site afterwards.

To delete the cache with one click you can install extensions for Firefox. 

*use at your own risk*

Empty Cache Button
Clear Cache Button
Clear Site Cache  

More Extensions for Firefox