You can remove all data stored in Firefox for a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History -> Show All History" or "View -> Sidebar -> History").

Using "Forget About This Site" will remove all data stored in Firefox for this domain like history and cookies and passwords and exceptions and cache, so be cautious. If you have a password or other data for that domain that you do not want to lose then make sure to backup this data or make a note.

You can't recover from this 'forget' unless you have a backup of involved files.

If you revisit a 'forgotten' website then data for that website will be saved once again.

• https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox

If that doesn't work then try to open the main Facebook website in a New Private Window.

This seems to be a problem with local storage and it looks that running this command as posted in bug 1569296 in the Web Console fixes it.

• localStorage.clear()

• "3-bar" menu button or Tools -> Web Developer
• https://developer.mozilla.org/en-US/Tools/Web_Console

• Bug 1569296 - Facebook pages loading blank

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)