It can be done if you first think about a mobile phone. Place the divs in the order you want them to appear in the small viewports, and then reorder them for the large viewports.
<div class="row"> <div class="col-sm-12 col-md-6 col-md-push-6"> <div style="background:red"> Put the one that for small screen on top </div> </div> <div class="col-sm-12 col-md-6 col-md-pull-6"> <div style="background:green"> Put the one that for small screen on bottom </div> </div> </div>
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