The error you receive may look like the following:
$ git push -u github.master > fatal: 'github.master' does not appear to be a git repository > fatal: The remote end hung up unexpectedly $ git pull -u github > error: SSL certificate problem, verify that the CA cert is OK. Details: > error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed while accessing https://github.com/tqisjim/google-oauth.git/info/refs > fatal: HTTP request failed
A "CA" is shorthand for a "certificate authority," a third-party group responsible for handling secure connections around the web. They establish digital "certificates," which are a way of ensuring that there are valid connections between two machines (like your computer and GitHub.com). Without a certificate, the security risk between two machines is greater.
When you receive this error, it likely means that your CA is out-of-date and needs to be updated. Generally, updating your operating system also updates your CA, and solves the problem.