From Spiffy Stores Knowledge Base

This template is rendered whenever a page or resource cannot be found.

If you do not provide a 404.liquid template in your theme, a default system template will be used instead.

<h1>Page not found <span class="not_found">404</span></h1>
<div class="textile">
  <p>Perhaps you want to return to the <a href="/">home page</a> or <a href="/search">try a search</a>.</p>


In 404.liquid you have access to all of the following variables: