Depends on the exact reasons the cert failed. There are cases where failing and Firefox does not display the accept dialog is the expected behavior.

In which version of Firefox are you having this issue: desktop, Android or iOS? (Your post is under Android but you're posting from iOS, so I thought I would ask.)

The more limited error page certainly is a known issue on iOS:

• Unable to display http so websites with self signed certs
• NSURLErrorDomain

I'm sorry for the wrong posting. I'm using brand new Firefox on iOS, just installed today. I receive the message described in the original post, followed by: NSURLErrorDomain Something I can do to accept the certificate ?

There is not a way to get around this currently on iOS.

Exact message is: "The certificate for this server is invalid. You might be connecting to a server that is pretending to be “MyDomainHere" which could put your confidential information at risk" I'm not certain what is the exact reason. I guess the web site was built using some Linux based site builder and it's running ok on Firefox on Windows (PC), i.e. It display the accept certificate dialog. Thanks in advance.

Thank you for your reply kbrosnan

The certificates failing does means that it can put your information at risk and I think it is not an option in Firefox for iOs to bypass this problem.

I'm having the same issue with a site where I have my own self-generated certificate. Obviously, I trust it. Could FireFox install a "Accept the risk" button in their iOS product? If not, can I import my certificate?