You can customize the 404 Error page that visitors see when they try to access a page that doesn’t exist on your site.
Make the design your own and add links to your site pages to make sure your visitors keep exploring.
To create a customized 404 error page:
Click Menus & Pages on the left side of the Editor.
Click Add Page at the bottom of the panel.
Select Error Page (404).
Hover over the page template you want to use and click Add Page.
Customize your page to match your site. Below are some ideas:
Change the text to match the voice and tone of your site
Add a site menu
Add links to popular sections of your site that your visitors might be looking for
Change the default image:
Click the 404 image.
Click Change Vector Art.
Click the All Categories drop-down menu and select Technology.
Choose another vector art.
6. Publish your site.