css

Use Boostrap, it introduces screen size dependent css classes. Boostraps grid divides the screen in 12 units. With this example you can have a screen layout that automatically stacks the divs if the screen width is below 768px.

<div class="container-fluid"> <div class="row">
<div class="col-sm-4" style="background-color:green;">.col-sm-4</div> <div class="col-sm-4" style="background-color:red;">.col-sm-4</div> <div class="col-sm-4" style="background-color:green;">.col-sm-4</div>
</div>
</div>