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TLS Certificates are the backbone of the World Wide Web's Public Key Infrastructure. In case of a compromise of private cryptographic keys, it is vital to have the ability to revoke certificates before their validity period expires. This paper describes and contrasts the two major mechanisms for certificate revocation - Certificate Revocation Lists (CRLs) and Online Certificate Status Protocol (OCSP). It is found that modern web clients and browsers such as Google Chrome do not perform stringent checking of certificate revocation status, leaving users open to attackers who use revoked certificates to spoof web sites and services. A browser extension is proposed and implemented for Google Chrome that checks CRL and OCSP status and notifies the user. It can also automatically navigate away from the page if the certificate is found to be revoked. The extension is created using JavaScript and uses a background process written in Python to handle the revocation checking. It is found to be able to complete CRL and OCSP requests for common websites in under a second, and under 200 milliseconds for locally cached responses. [ABSTRACT FROM AUTHOR]