Minor typo fix

README.md

@@ -18,7 +18,7 @@ Our latest and greatest source of Jenkins CI can be found on [GitHub]. Fork us!
 
 News and Website
 ----------------
-All about Jenkins CI can be found on our [website]. Follow us an Twitter @[jenkinsci].
+All about Jenkins CI can be found on our [website]. Follow us on Twitter @[jenkinsci].
 
 [ButlerImage]: http://jenkins-ci.org/sites/default/files/jenkins_logo.png
 [MIT License]: https://github.com/jenkinsci/jenkins/raw/master/LICENSE.txt