Center all the things in css http://html5hub.com/centering-all-the-directions/#i.p7j5a41ejida9s

center-all-the-things.css

  #ex3_container { width:200px; height:200px; background-color:yellow; position:relative; }
  #ex3_content { left:50%; top:50%; transform:translate(-50%,-50%); 
                -webkit-transform:translate(-50%,-50%); 
                background-color:gray; color:white; position:absolute; }