Question 1

What is an SSL/TLS certificate?

Accepted Answer

An SSL/TLS certificate is a digital certificate issued by a trusted Certificate Authority (CA). It verifies a website's identity and enables an encrypted connection between the browser and the server. A site without a valid certificate cannot offer secure HTTPS access.

Question 2

What happens when a certificate expires?

Accepted Answer

Once a certificate expires, browsers show visitors a warning such as "Your connection is not private", and most users leave. Search engines may also downrank expired sites, so renew within 30 days before expiry.

Question 3

How is the security grade calculated?

Accepted Answer

The grade is based on facts from Certificate Transparency logs: whether the certificate is currently valid and its remaining lifetime. An expired certificate results in an F.

Question 4

Why does it say "could not establish a TLS connection"?

Accepted Answer

It means no certificate records for this domain were found in Certificate Transparency logs. Common causes: HTTPS is not enabled on the site, the domain does not exist, or the certificate data source is temporarily unavailable.