hello velcroman, what's the address of the site you're trying to access?

Thank you for your quick response. The address is https://www.fanfiction.net

ok, i can certainly replicate this issue. my guess is that the site is currently implementing measures against the recently published widespread vulnerability that allows webservers with a certain version of openssl running on them to be exploited (heartbleed.com) & is switching their certificate.

an advanced security feature in firefox is picking up this change as the site doesn't seem to be fully updated for this new certificate yet. you can temporarily work around the issue:
enter about:config into the firefox address bar (confirm the info message in case it shows up) & search for the preference named security.ssl.enable_ocsp_stapling. double-click it and change its value to false.
it is important however, that after a bit of time when the issue gets resolved by the site (maybe try again in 24 hours), you go back and switch the setting to "true" again!

I had this problem too but this fixed it. Thank you!

That worked. Thank you.

you're very welcome - the issue seems to have been fixed at the site already, so you can go ahead and set security.ssl.enable_ocsp_stapling back to true again.

I cannot get into Mozilla.com or Firefox and I keep getting 'Untrusted site' messages. I have, many times, deleted the cert8 files and reboot but it still doesn't work. I cannot get my email or FB on Firefox. Everything works very well on Google Chrome so I know it's not me. I have run my AVG virus/malware programs and scanned the computer a couple of times; still no luck with Mozilla.com or Firefox.com. Sometimes I can get by the Untrusted site with some websites but not Yahoo.com. It comes in a long list with no access for me to see my mail. This is Google Chrome I am using now and I am not keen on it. I have used Firefox for years and it works perfectly on my other laptop. What gives?? I really need help. PS. I get the 'Untrusted site' on ALL the sites I try to access including Google search, Google.com, Firefox.com, Mozilla.com and aol and yahoo and Facebook. I didn't try any others so it isn't a security prob. It's a Firefox problem on my computer.

I am having the untrusted web site on almost everything using w7. I can not even open a Firefox web site. I am writing this on IE because of all of this. Firefox works just fine on my laptop. Firefox has become usless to me unless this can be fixed. Bill in Texas

PS I have already tried most of the recommended fixes

hello billintexas, this question you're posting to dealt with the error when it only showed up on one particular page (and the issue already got resolved by the site). if you get the error on all secure/encrypted pages, please open a new question for that issue and inclde details like the error code that is shown thank you!