"You don't have permission to access..." errors are characteristic of a firewall that protects the server against misuse and this firewall thinks something is suspicious about the HTTP request. If you use a proxy or VPN then try to use a direct connection. You can try to clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences) to see if that fixes it. I've also seen cases where having "Resist Fingerprinting" enabled caused this issue to occur.

• https://support.mozilla.org/en-US/kb/firefox-protection-against-fingerprinting

If this all doesn't work then you can try "Forget About This Site" in the right-click context menu of an history item.

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

Thanks cor-el

A clear and concise set of instructions for getting rid of this website bloc. Simply deleting the history in fact did it for me; I tried the easiest first.

This problem comes up for me every six months or so, usually with a website I had been successfully accessing for years. Be nice if the error message could guide one to the culprit that is blocking the site rather than just sending an unintelligible error number. . many thnaks for your care, Will Gasser

What Firefox displays is what is send by the website when they think that something is unusual about the request, Firefox can only display the server response.