tricki

if (document.querySelector('#grid-preview')) {
  document.querySelector('#grid-preview').remove();
  document.querySelector('#grid-preview-style').remove();
} else {
  document.body.insertAdjacentHTML('beforeend', '<div class=container id=grid-preview><div class=row><div class=col><div class=inner><div class="d-block d-sm-none">XS</div><div class="d-none d-md-none d-sm-block">SM</div><div class="d-none d-lg-none d-md-block">MD</div><div class="d-none d-lg-block d-xl-none">LG</div><div class="d-none d-xl-block d-xxl-none">XL</div><div class="d-none d-xxl-block">XXL</div></div></div><div class=col><div class=inner></div></div><div class=col><div class=inner></div></div><div class=col><div class=inner></div></div><div class=col><div class=inner></div></div><div class=col><div class=inner></div></div><div class=col><div class=inner></div></div><div class=col><div class=inner></div></div><div class=col><div class=inner></div></div><div class=col><div class=inner></div></div><div class=col><div class=inner></div></

trey

/* http://twitter.github.com/bootstrap/scaffolding.html#responsive */

/* Landscape phones and down */
@media (max-width: 480px) { ... }

/* Landscape phone to portrait tablet */
@media (max-width: 768px) { ... }

/* Portrait tablet to landscape and desktop */
@media (min-width: 768px) and (max-width: 940px) { ... }