title: Accidently removed Digicert certificate from mac
body: <p>After I upgraded my macbook air to latest version of Mac 10.9.2
  I was constantly being rejected from accessing Github, with a strange error page showing 'certificate invalid'.</p>
  
  <p>I tried to google for the solution, and found a post telling others to remove Digicert certificate from the keychain application.</p>
  
  <p>As a happy reader, I applied the solution and the problem was safely gone away, at least I thought so.</p>
  
  <p>Although I was able to access github page without previous error,
  a new error cropped up, "Failed to load resource::ERR_INSECURE_RESPONSE".
  I was able to load the content of the page perfectly, but at the same time, wasn't able to load related css and js file due to the aforementioned error.</p>
  
  <p>After messing around with some quick google searches,
  I am guessing the action of deleting Digicert certificate to be the root problem,
  and want to restore the certificate.</p>
  
  <p>Am I guessing right?
  If not, what should I do to resolve this problem?
  If yes, how can I restore the Digicert certificate?</p>
  
  <p>Note:
  I am using Google Chrome as a browser.</p>