Safari 5.1 (OS X Lion): Certificates and secure websites
A certificate is a file that helps keep web communications secure. It’s also known as a digital certificate and public key certificate.
Certificates are issued by trusted organizations, such as VeriSign, Inc. or RSA Security, Inc. When you use Safari to visit a secure webpage—for example, to do online banking—Safari checks the site’s certificate and compares it with certificates that are known to be legitimate. If Safari doesn’t recognize the website’s certificate, or if the site doesn’t have one, Safari lets you know.
Some websites have extended validation certificates, also know as “EV certificates,” which require more extensive investigation by the certifying agencies. Safari supports EV certificates.
A secure website and Safari work together to encrypt any information you exchange with the site. The key used for the encryption is contained in the site’s security certificate. No one can read the information as it’s being sent. This protects your login information, credit card numbers, addresses, and other secure data.
If you need to connect to a website that requires a personal certificate, you are provided with a certificate and instructions for installing it. Once your certificate is installed, you can gain authenticated access to the website automatically. If you are unable to access the website, contact the website administrator.