bootstrap_ms.css

.col-ms-1,
.col-ms-2,
.col-ms-3,
.col-ms-4,
.col-ms-5,
.col-ms-6,
.col-ms-7,
.col-ms-8,
.col-ms-9,
.col-ms-10,
.col-ms-11,
.col-ms-12 {
  position: relative;
  min-height: 1px;
  padding-left: 15px;
  padding-right: 15px; }

@media (min-width: 480px) {
  .col-ms-1,
  .col-ms-2,
  .col-ms-3,
  .col-ms-4,
  .col-ms-5,
  .col-ms-6,
  .col-ms-7,
  .col-ms-8,
  .col-ms-9,
  .col-ms-10,
  .col-ms-11 {
    float: left; }

  .col-ms-1 {
    width: 8.33333%; }

  .col-ms-2 {
    width: 16.66667%; }

  .col-ms-3 {
    width: 25%; }

  .col-ms-4 {
    width: 33.33333%; }

  .col-ms-5 {
    width: 41.66667%; }

  .col-ms-6 {
    width: 50%; }

  .col-ms-7 {
    width: 58.33333%; }

  .col-ms-8 {
    width: 66.66667%; }

  .col-ms-9 {
    width: 75%; }

  .col-ms-10 {
    width: 83.33333%; }

  .col-ms-11 {
    width: 91.66667%; }

  .col-ms-12 {
    width: 100%; }

  .col-ms-push-1 {
    left: 8.33333%; }

  .col-ms-push-2 {
    left: 16.66667%; }

  .col-ms-push-3 {
    left: 25%; }

  .col-ms-push-4 {
    left: 33.33333%; }

  .col-ms-push-5 {
    left: 41.66667%; }

  .col-ms-push-6 {
    left: 50%; }

  .col-ms-push-7 {
    left: 58.33333%; }

  .col-ms-push-8 {
    left: 66.66667%; }

  .col-ms-push-9 {
    left: 75%; }

  .col-ms-push-10 {
    left: 83.33333%; }

  .col-ms-push-11 {
    left: 91.66667%; }

  .col-ms-pull-1 {
    right: 8.33333%; }

  .col-ms-pull-2 {
    right: 16.66667%; }

  .col-ms-pull-3 {
    right: 25%; }

  .col-ms-pull-4 {
    right: 33.33333%; }

  .col-ms-pull-5 {
    right: 41.66667%; }

  .col-ms-pull-6 {
    right: 50%; }

  .col-ms-pull-7 {
    right: 58.33333%; }

  .col-ms-pull-8 {
    right: 66.66667%; }

  .col-ms-pull-9 {
    right: 75%; }

  .col-ms-pull-10 {
    right: 83.33333%; }

  .col-ms-pull-11 {
    right: 91.66667%; }

  .col-ms-offset-1 {
    margin-left: 8.33333%; }

  .col-ms-offset-2 {
    margin-left: 16.66667%; }

  .col-ms-offset-3 {
    margin-left: 25%; }

  .col-ms-offset-4 {
    margin-left: 33.33333%; }

  .col-ms-offset-5 {
    margin-left: 41.66667%; }

  .col-ms-offset-6 {
    margin-left: 50%; }

  .col-ms-offset-7 {
    margin-left: 58.33333%; }

  .col-ms-offset-8 {
    margin-left: 66.66667%; }

  .col-ms-offset-9 {
    margin-left: 75%; }

  .col-ms-offset-10 {
    margin-left: 83.33333%; }

  .col-ms-offset-11 {
    margin-left: 91.66667%; } }
@media (min-width: 480px) and (max-width: 768px) {
  .container {
    max-width: 748px; } }

At line 18 change the code to this :

@media (min-width: 480px) and (max-width: 768px) {

Thanks for this @andyl.

Just a note that I find it hard to distinguish between .col-sm-* and .col-ms-* when both are used in the same markup.

I decided to rename the new classes to .col-sr-*, where sr stands for "smaller", thus smaller than small (sm), but larger than extra small (xs). Well, it makes sense in my head at the moment.