Initial AD port

themes/after-dark/docs/content/feature/error-page.md

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+title = "Error Page"
+description = "Give visitors a reason to stay when errors occur."
+categories = ["experience"]
+tags = ["engagement", "retention", "branding"]
+features = ["error page", "snippets", "code highlighter", "related content", "index blocking"]
+[[copyright]]
+  owner = "Josh Habdas"
+  date = "2019"
+  license = "agpl-3.0-or-later"
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+
+After Dark includes an animated {{< external rel="nofollow help" href="/404.html" text="404 Page" />}} you can display when other pages cannot be found. The error page contains a full-screen background animation and "404" link with Ginsu treatment. Following the link navigates to the homepage.
+
+{{< hackcss-card header="Interactive Example" >}}
+  <iframe title="Error Page Example" width="100%" height="300" src="/404.html"></iframe>
+{{< /hackcss-card >}}
+
+<!--more-->
+
+Adjust it from `404.html` in the site `content` directory:
+
+```
+├── archetypes
+├── content
+│   ├── post
+│   └── 404.html
+├── layouts
+```
+
+If the file doesn't exist yet, copy it from the theme default:
+
+```sh
+$ cp themes/after-dark/content/404.html content
+```
+
+Configure your web server to redirect to `404.html` when pages cannot be found to use it. Combine with [Voyeur Module](/module/voyeur) for help creating {{< external href="https://gohugo.io/content-management/urls/#aliases" text="Page Aliases" />}}.