Bootstrap 3 - Column Collapse Order - http://scotch.io/bar-talk/bootstrap-3-tips-and-tricks-you-might-not-know#column-collapse-order

bootstrap3-Column-Collapse.html

<!--
Desktop:
    [1 2 3] [1 2 3 4 5 6 7 8 9]

Mobile:
    [1 2 3]
    [1 2 3 4 5 6 7 8 9]
-->
<div class="row">
   <div class="col-md-9 col-md-push-3">1 2 3 4 5 6 7 8 9 </div>
   <div class="col-md-3 col-md-pull-9">1 2 3 </div>
</div>

 <!--
Desktop:
    [ 2nd col ] [ 1st col ]

Mobile:
    [ 2nd col ]
    [ 1st col ]
-->
<div class="row">
   <div class="col-md-6 col-md-push-6">1st col</div>
   <div class="col-md-6 col-md-pull-6">2nd col</div>
</div>