Custom 404 pages
How to add a custom 404 not found page to your site
You can override the default 404 page for your Wunderbucket site by creating a _404.html file at the root of your site's folder.
Any time someone visits a url on your site that returns a 404 response, they'll see the contents of your _404.html page.
If you want to go back to the default Wunderbucket 404 page, just delete the file and re-publish your site.