<div class="container">
<h1>:(</h1><br>
<h2>A <span>404</span> error occured, Page not found, check the URL and try again.</h2><br><br>
  <h3><a href="#">Return to home</a>&nbsp;|&nbsp;<a href="javascript:history.back()">Go Back</a></h3>
</div>
@import url('https://fonts.googleapis.com/css?family=Montserrat:300');
body{
  background: #3498DB;
  color: #fff;
  font-family: 'Montserrat', sans-serif;
  font-size: 16px;
}
h1{
  font-size: 30vh;
}
h2 span{
  font-size: 4rem;
  font-weight: 600;
}
a:link, a:visited{
  text-decoration: none;
  color: #fff;
}
h3 a:hover{
  text-decoration: none;
  background: #fff;
  color: #3498DB;
  cursor: pointer;
}

External CSS

  1. https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.3/css/bootstrap.min.css

External JavaScript

This Pen doesn't use any external JavaScript resources.