@media all and (max-width: 768px) {
  .view-portfolio.view-display-id-page_2 .view-content .views-row {
    width: 100%;
    max-width: 450px;
    margin:5% auto;
  }
}

@media all and (min-width: 768px) and (max-width: 959px) {
  .view-portfolio.view-display-id-page_2 .view-content .views-row {
    width: 49%;
    float: left;
  }
  .view-portfolio.view-display-id-page_2 .view-content .views-row:nth-child(2n - 1) {
    margin-right: 2%;
  }
}

@media all and (min-width: 960px) {
  .view-portfolio.view-display-id-page_2 .view-content .views-row {
    float: left;
    width: 49%;
  }
  .view-portfolio.view-display-id-page_2 .view-content .views-row:nth-child(2n - 1) {
    margin-right: 2%;
  }
}