.header{
  text-align: center;
}

.row .col-md-4{
  display: block;
  width: 100%
}

a.internal{
  text-decoration: none;
  color: #337ab7;
}

a.internal:hover{
  text-decoration: underline;
}

@media (min-width: 840px){
  .row .col-md-4{
    display: inline-block;
    width: 33%;
  }
}