he SSL certificate is trusted if it is signed by a "trusted" or pre-installed root certificate. As an established, globally recognized certificate authority, Symantec, Thawte and Geotrust root certificates are pre-installed in most major browsers.
The SSL certificate is valid if it has not expired or been revoked. Certificate authorities manage a Certificate Revocation List (CRL) used by browsers to check validity. Newer browsers have adopted Online Certificate Status Protocol (OCSP), a faster, more efficient way to verify certificate status. Symantec, Thawte and Geotrust have a global infrastructure that handles 6 billion OCSP look ups every day.
The domain name in the certificate matches the domain name of the site being accessed. Symantec, Thawte and Geotrust verify the domain name as well as the applicant or organization’s control of the domain name before issuing the certificate.
If any of the checks fail, an alert is generated in real-time to the user who decides whether to proceed, cancel the session or view the SSL certificate. To prevent security alerts from undermining trust in your site, select an SSL certificate from a recognized Certificate Authority.