Do you use a bookmark or are you starting with the main (home) page of this website?

If you use a bookmark to access a specific page then instead navigate to this page starting with the main page or with the sign in page in case there is a problem with this bookmark.

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

There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connection certificates and send their own.

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message

https://support.mozilla.org/en-US/kb/connection-untrusted-error-message

Websites don't load - troubleshoot and fix error messages

http://kb.mozillazine.org/Error_loading_websites

What do the security warning codes mean

cor-el: I've seen this response before. It is not helpful. First, the same problem happens if I use a bookmark or if I start with a fresh Firefox page, with all history cleared. Second, the "Forget About This Site" option does not exist on my current version of Firefox (version 92.0.1), at least not through the "History -> Show All History" or "View" links, which also do not exist.

FredMcD: I'm not using any of the security software you mentioned. And sending me a shotgun blast of links that have nothing to do with this specific problem is also not helpful (especially sending me a link pertaining to Firefox versions 43 and below when I'm using a current version). One of the links wouldn't even load into Firefox; it must be so old it's irretrievably corrupted, or doesn't even exist anymore.

Can someone please help with a current solution to my specific problem?

Thanks in advance.

Easiest is to open the History sidebar (Ctrl+H) and search for this domain. If you right-click such an history item then you should find "Forget About This Site".

cor-el: I followed your instructions, found the "Forget About This Site" button and used it to "forget" the penfed.org webpage, BUT, it did not fix my problem. Any other suggestions?

This can happen if the website thinks that there is something unusual about your request. This can be a customization you make like blocking content/cookies or about an extension or about security software that interferes or different.

What security software do you have?

Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or userChrome.css is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

FredMcD: One of the links wouldn't even load into Firefox

Thank you. I tested and updated my information.