<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>
<script src="https://cdnjs.cloudflare.com/ajax/libs/magnific-popup.js/1.1.0/jquery.magnific-popup.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/mixitup/2.1.11/jquery.mixitup.min.js"></script>
<div class="container">
<div class="row">
<div class="col-md-4">
<div class="section-title">
<h2>Portfolio</h2>
</div>
</div>
<div class="col-md-8">
<div class="portfolio-menu">
<button type="button" data-filter="all">All</button>
<button type="button" data-filter=".category-a">Bootstrap</button>
<button type="button" data-filter=".category-b">HTML5</button>
<button type="button" data-filter=".category-c">CSS3</button>
<button type="button" data-filter=".category-d">JS</button>
</div>
</div>
</div>
</div>
<div class="container">
<div id="container" class="row">
<div class="col-md-4 mix category-a">
<div class="single-portfolio">
<a class="gallery-item" href="https://static.pexels.com/photos/402023/pexels-photo-402023.jpeg"><img class="img-responsive" src="https://static.pexels.com/photos/402023/pexels-photo-402023.jpeg" alt="One" /></a>
</div>
</div>
<div class="col-md-4 mix category-b">
<div class="single-portfolio">
<a class="gallery-item" href="https://static.pexels.com/photos/402023/pexels-photo-402023.jpeg"><img class="img-responsive" src="https://static.pexels.com/photos/402023/pexels-photo-402023.jpeg" alt="One" /></a>
</div>