hi, what kind of error code is shown when you click on the "advanced" button?

"www.google.com uses an invalid security certificate. The certificate is not trusted because the issuer certificate is unknown. The server might not be sending the appropriate intermediate certificates. An additional root certificate may need to be imported. (Error code: sec_error_unknown_issuer)"

Note that the original (non-advanced) error message says that an exception is not allowed.

Except for the site name, Yahoo and Google error messages are identical.

This also affects my gmail account. I am guessing it applies to all secure (https) sites.

thanks, this might be caused by something on your system/network intercepting secure connections. please refer to How to troubleshoot security error codes on secure websites for the most common solutions for this issue.

Thanks, philipp! That took care of the problem.