Which page is "this page"?

Thanks the-edmeister for looking into this! Much appreciated on such short notice on holidays!!!

The page is a forum run and issues reported were only with Firefox for the last two weeks. Hence my post here. In the meantime the issue has affected other browsers as well. So I don't think this is related to Firefox anymore.

Case closed. Thanks again!

If the site has NO sections that use HTTPS, it's puzzling that anyone would try using HTTPS with the site in the first place. However, if the site has SOME sections that use HTTPS, a possible issue is if those sections set a flag to ALWAYS use HTTPS. You can tell that's the problem in Firefox because the error page will mention you can't create an exception due the HSTS or "Strict Transport Security." At least that gives you something to look for.

How are you browsing to that page?

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

If you use a bookmark or use a link that has specific GET data appended to the link or a page that has been requested by sending a form with POST data to open a specific page on the server then try to navigate to that page starting with the main page or the sign in page in case this bookmark/link is currently broken. If you use a bookmark then try to navigate to that page starting with the main page or the sign in page in case there is a problem with this bookmark.

Clear the cache and remove the cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Clear the cache":

• Firefox/Options/Preferences -> Advanced -> Network -> Cached Web Content: "Clear Now"

"Remove the cookies" from websites that cause problems.

• Firefox/Options/Preferences -> Privacy -> "Use custom settings for history" -> Cookies: "Show Cookies"