<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<div class="calculator container">
<div class="row">
<h2>Calculator</h2>
</div>
<div class="row">
<div class="outputBox" contenteditable></div>
<div class="buttonContainer">
<div class="row">
<div class="col-xs-2">
<button class="numberButton" type="button">7</button>
<button>8</button>
<button>9</button>
</div>
</div>
<div class="row">
<div class="col-xs-2">
<button>4</button>
<button>5</button>
<button>6</button>
</div>
</div>
<div class="row">
<div class="col-xs-2">
<button>1</button>
<button>2</button>
<button>3</button>
</div>
</div>
<div class="row">
<div class="col-xs-2">
<button class="zeroButton">0</button>
<button>=</button>
