Check out why the site is untrusted (click "Technical Details to expand that section) and if this is caused by a missing intermediate certificate then see if you can install this intermediate certificate from another source.

You can retrieve the certificate and check details like who issued certificates and expiration dates of certificates.

• Click the link at the bottom of the error page: "I Understand the Risks"

Let Firefox retrieve the certificate: "Add Exception" -> "Get Certificate".

• Click the "View..." button and inspect the certificate and check who is the issuer of the certificate.

You can see more Details like intermediate certificates that are used in the Details pane.

If "I Understand the Risks" is missing then this page may be opened in an (i)frame and in that case try the right-click context menu and use "This Frame: Open Frame in New Tab".

the problem is not with an untrusted cert. the problem is what firefox does when there IS an untrusted cert, and the URL contains an IPv6 address literal (e.g. https://[2001:470:3d:100::120]). There is a bug that prevents me from overriding the warning and saying "connect anyway". This works fine with an IPv4 address literal (I can tell it to connect anyway over IPv4). Also if the URL contains a domain name (e.g. https://www.sixscape.com) that happens to resolve to an IPv6. The problem is only when the URL contains an IPv6 address literal. This is easy to reproduce.

Also, there is no problem doing this in any version of IE.