diff --git a/docs/src/pages/core-concepts/astro-pages.md b/docs/src/pages/core-concepts/astro-pages.md
index de61239c8..1657be290 100644
--- a/docs/src/pages/core-concepts/astro-pages.md
+++ b/docs/src/pages/core-concepts/astro-pages.md
@@ -58,3 +58,8 @@ console.log(data);
 <!-- Output the result to the page -->
 <div>{JSON.stringify(data)}</div>
 ```
+
+## Custom 404 Error Page
+
+For a custom 404 error page create a `404.astro` file in `/src/pages`. That builds to a `404.html` page. Most [deploy services](/guides/deploy) will find and use it.  
+This is special and different to the default behavior building `page.astro` (or `page/index.astro`) to `page/index.html`.