Firefox error using OFBiz demo certificate

I had issues running OFBiz in Firefox 3.0.8 (but the problem may be already there since 3.0.3) on MacOSX; the browser was returning the following error:

Error code: sec_error_expired_issuer_certificate

I managed to fix it following these steps:
1) Firefox-> preferences -> advanced -> encryption -> view certificates -> servers
2) Add exception...
3) Enter https://localhost:8443