<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="/lib/bootstrap.min.css">
<script src="/lib/jquery-1.12.2.min.js"></script>
<script src="/lib/bootstrap.min.js"></script>
</head>
<body>
<div class="container-fluid">
<h1>Hello World!</h1>
<div class="row">
<div class="col-xs-6 col-sm-3" style="background-color:lavender;">
Column 1<br>
Resize the browser window to see the effect. Also try to remove the div clearfix line and see what happens.
</div>
<div class="col-xs-6 col-sm-3" style="background-color:lavenderblush;">Column 2</div>
<!-- Add clearfix for only the required viewport -->
<div class="clearfix visible-xs"></div>
<div class="col-xs-6 col-sm-3" style="background-color:lightcyan;">Column 3</div>
<div class="col-xs-6 col-sm-3" style="background-color:lightgray;">Column 4</div>
</div>
</div>
</body>
</html>