In FireFox 3 it makes you jump through hoops to allow you access a site which has self-signed certificates or has one with an unknown issuer such as CAcert.
The FF3 developers regard this as a feature as it may help prevent potential man-in-the-middle attacks or people making false assumptions about sites based on a padlock by making you add exceptions in every case. I personally regard this functionality as an extremely irritating flaw in FF3 that it goes out of its way to annoy, provides an utterly inadequate explanation for the end user and gets in the way of lots of legitimate use cases (think passwords on non-critical sites that would otherwise be sent in plaintext using http where /any/ security even without trust is actually an improvement). What's even more annoying is that I've yet to find a good way of getting around this broken functionality.
The FF3 developers regard this as a feature as it may help prevent potential man-in-the-middle attacks or people making false assumptions about sites based on a padlock by making you add exceptions in every case. I personally regard this functionality as an extremely irritating flaw in FF3 that it goes out of its way to annoy, provides an utterly inadequate explanation for the end user and gets in the way of lots of legitimate use cases (think passwords on non-critical sites that would otherwise be sent in plaintext using http where /any/ security even without trust is actually an improvement). What's even more annoying is that I've yet to find a good way of getting around this broken functionality.