Checking if a Certificate is Valid

[DavidGreenberg]

SSL/TLS certificates can be validated through a number of different methods and tools.  This includes using CURL or using any online SSL check tool.

Testing a TLS/SSL connection: 
openssl s_client -connect www.examplesite.com:443 -servername www.examplesite.com

Spoof a host-header using cURL: 
curl -I https://d8wc7770wud0x.cloudfront.net/ -H "Host: www.examplesite.com"

SSL Labs:
https://www.ssllabs.com/ssltest/

DigiCert:
https://www.digicert.com/help/

Details of the cert can also be viewed through Google Chrome or other developer tools.  
Chrome:

1. Go to site
2. Hit F12 to access developer tools.
3. Click on Security tab
4. Click on View Certificate