Trusted (Standard Validation)
Trusted (Extended Validation)
Trusted (Unicode characters in certificate e.g. company name)
Trusted (Expired certificate with external timestamp made within validity of certificate)
Trusted (Self-Signed certificate manually added to Trusted list)
Trusted (Weak hash)
Trusted (WHQL verified)

Untrusted (No certificate)
Untrusted (Certificate revoked)
Untrusted (Certificate expired and not timestamped)
Untrusted (Certificate expired and timestamped outside of validity period of certificate)
Untrusted (Certificate expired and timestamped by a non-trusted authority)
Untrusted (File Contents tampered with)
Untrusted (Self-signed, not trusted)
Untrusted (Insufficiently long key)
Untrusted (Certificate is issued in the same company name, by a Trusted CA, but company is registered in another country and is not your real company)
Untrusted (Malicious use of multiple certificates, some of which are invalid)

Other (Computer clock is wrong)