.one-third-column {
  width:32%;
  margin-right:2%;
  float:left;
}
.one-third-column-last {
  width:32%;
  margin-right:0;
  float:right;
}

.one-third-column h3, .one-third-column-last h3 {
  margin-top: 1rem;
}

@media only screen and (max-width: 600px) {
  .one-half-column-left, .one-half-column-right, 
  .one-third-column, .one-third-column-last {
    float:none;
    width:100%;
    margin-right:0;
  }
}