There are TLS settings prefs on the about:config page that specify the minimum and maximum TLS version.

• security.tls.version.min = 1
• security.tls.version.max = 3
• 1 means TLS 1.0; 2 means TLS 1.1; 3 means TLS 1.2; 4 means TLS 1.3;
• http://kb.mozillazine.org/security.tls.version.

Your security software may be acting as a man-in-the-middle and may not support TLS 1.2/1.3 yet.

You can check your browser.

• https://www.ssllabs.com/ssltest/viewMyClient.html

See also whether your security software is covered in this article:

• https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message#w_avast-and-avg-security-products
• https://support.mozilla.org/en-US/kb/troubleshoot-SEC_ERROR_UNKNOWN_ISSUER

It is possible that there is a temporary problem on that website.

Can you attach a screenshot?

• https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem
• use a compressed image type like PNG or JPG to save the screenshot

You can remove all data stored in Firefox from 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 from this domain like history and cookies and passwords and exceptions and cache, so be cautious. If you have a password or other data from 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 from that website will be saved once again.

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

Thank you for trying to help me but this solution sounded way too complicated for me....remember, I know next to nothing about how a computer works. But, good news, the 7 Little Words site appeared this morning after my second attempt to get in! So, many thanks for your suggestion and the time you spent on the answer!

Thank you for your reply and I do appreciate you taking the time to help me out. Your suggestion sounded much too complicated for someone like me who knows next to nothing about computers. But, on the bright side, the site I was trying to reach (7 Little Words) magically appeared after my second attempt this morning.

Nevertheless, many thanks.