update design

public/partials/404.htm

@@ -1,5 +1,17 @@
-<div class="container d-flex h-100">
-  <h1 class=" m-auto text-center">
-    <div class="display-1">404</div><small class="text-muted">Page not found</small>
-  </h1>
+<div class="paper-empty">
+  <div class="paper-empty-inner">
+    <div class="paper-eyebrow">Error &middot; 404</div>
+    <h1 class="paper-empty-title">
+      This link<br /><em>isn&rsquo;t here.</em>
+    </h1>
+    <p class="paper-empty-lede">
+      The anonymous mirror you&rsquo;re looking for has expired, been removed
+      by its owner, or never existed. If you received this URL from an
+      author, ask them to re-issue it.
+    </p>
+    <div class="paper-empty-cta">
+      <a href="/" class="btn-hero">Back to home</a>
+      <a href="/faq" class="btn-hero-ghost">Read the FAQ</a>
+    </div>
+  </div>
 </div>