What are the contents of a certificate and how can I view it?
HTTPS/TLS uses X.509 certificates generally. There is more detail here in the latest TLS specification.
You can view HTTPS certificates in a browser.
As per Wikipedia:
The structure of an X.509 v3 digital certificate is as follows:
Certificate

Version Number
Serial Number
Signature Algorithm ID
Issuer Name
Validity period

Not Before
Not After


Subject name
Subject Public Key Info

Public Key Algorithm
Subject Public Key


Issuer Unique Identifier (optional)
Subject Unique Identifier (optional)
Extensions (optional)

Certificate Signature Algorithm
Certificate Signature