Forget about any complicated way, just use Flexbox and set up horizontal center and vertical center in the container.
http://gengns.com/wp-content/uploads/2015/05/logo-onepage-300x66.png00Génesishttp://gengns.com/wp-content/uploads/2015/05/logo-onepage-300x66.pngGénesis2017-07-03 12:59:492017-07-03 12:59:49Horizontal and vertical center made easy
http://gengns.com/wp-content/uploads/2015/05/logo-onepage-300x66.png00Génesishttp://gengns.com/wp-content/uploads/2015/05/logo-onepage-300x66.pngGénesis2017-06-13 00:26:502017-06-13 00:29:43Footer with right and left buttons