app/templates/404.hbs
<ApplicationHeader />
<div class="wrapper">
<div class="landing-header" style={{html-safe (concat 'background-image: url(' (cdn-url) '/images/404.png);')}}/>
<div class="section section-white">
<div class="row row-section">
<div class="container-fluid">
<div class="col-md-8 col-sm-offset-2">
<BsAlert @dismissible={{false}} @type="warning">
The page was not found.
</BsAlert>
</div>
</div>
</div>
</div>
</div>