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

   In the main menu of the browser 

select "History" and below that the

submenu-item "Clear Recent History..."
   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.
   To delete all cache data, select 

"Everything" from the drop-down menu.

   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".

   With a click on the button "Clear now" 

you delete the cache.

   Reload the site afterwards.

If you use Sync then best is to disconnect Sync temporarily during troubleshooting.

You can check for problems with the places.sqlite and favicons.sqlite files in the Firefox profile folder.

• use "Verify Integrity" button on the "Help -> Troubleshooting Information" (about:support) page

In case errors are reported with "Verify Integrity" close and restart Firefox and retry.

If "Verify Integrity" cannot repair places.sqlite, rename/remove all places.sqlite and favicons.sqlite files in the Firefox profile folder. Firefox will rebuild places.sqlite and restore the bookmarks from a recent JSON backup in the bookmarkbackups folder.

• keep a backup copy of places.sqlite in case a new places.sqlite database has to be created

See also:

• https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file
• https://support.mozilla.org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Folder/Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/Profiles