Firefox won't block you from visiting HTTP websites. You can visit them all you want.

Can you please post the exact message you get?

Firefox 51+ will show "Connection is Not Secure" if you click the Control Center 'i' button at the left end of the location/address bar.

Note that this message is meant as a warning that you could be vulnerable and that it shouldn't prevent (block) you from accessing the website.

You can press the ESC key to close a doorhanger with a warning message in the name and password field.

See also:

• https://support.mozilla.org/en-US/kb/insecure-password-warning-firefox
• https://support.mozilla.org/en-US/kb/how-do-i-tell-if-my-connection-is-secure
• https://support.mozilla.org/en-US/kb/what-does-your-connection-is-not-secure-mean

Thanks for jumping in, Tyler! FF isn't giving me a message, it's redirecting me to a page that says (may not be exact wording but very close) "Firefox has determined that this site is not secure and has blocked it for your protection." Other statement says that I cannot override this. It's happened several times, most recently this morning right before I complained about it here. It's especially irritating because it's always sites for established mfrs or vendors that I've had bookmarked for years because I frequently either go to them or include the URL in a forum reply and have never had a problem loading them until the last few FF updates. Suddenly my bookmark no longer works. And this is just one of an increasing number of "upgrades" in the last couple of years

Fwiw, I've used FF since the days it was Netscape except for a hiatus after AOL bought NS and made it inuseable. But its increasing focus on protecting every user from every danger that might be lurking on the 'net whether we all need that much protection or not has made it increasingly aggravating to use in the last couple of years.

peggie said

FF isn't giving me a message, it's redirecting me to a page that says (may not be exact wording but very close) "Firefox has determined that this site is not secure and has blocked it for your protection."

Could you check the address bar above the error page: did Firefox try to retrieve the page over HTTPS instead of over HTTP?

There are typically three ways that could happen:

(1) The website sent a redirect

(2) An extension like HTTPS Everywhere "upgraded" the connection (but this doesn't always work)

(3) The site is on a list of sites that should only be loaded on an HTTPS connection