app/views/errors/not_found.html.erb
<h4>The page you were looking for doesn't exist.</h4>
<p>You may have mistyped the address or the page may have moved.</p>
<p>Try searching again, use <%= link_to 'advanced search', 'https://catalog.libraries.psu.edu/advanced' %>, or check out our <%= link_to 'search tips page', 'https://catalog.libraries.psu.edu/search_tips' %> to learn more about finding things in the catalog. If you need more assistance, <%= link_to 'Ask a Librarian', 'https://libraries.psu.edu/ask/' %>.</p>