.viewport{margin-top: 30px; margin-bottom: 30px; margin-right: auto;margin-left: auto;}@media (min-width: 768px){.viewport{width: 750px}}@media (min-width: 992px){.viewport{width: 970px}}@media (min-width: 1200px){.viewport{width: 1170px}}.viewport-fluid{margin-right: auto;margin-left: auto;}