When you change your website, more specifically re-arranging the structure of you website: it’s possible that some page (urls) will still be indexed by Google whilst the url itself does not exist any longer.

In a perfect world, you try to map these old urls to the new relevant ones. E.g. using a redirect plugin (301).
If the ‘old urls’ don’t have an equivalent page, WordPress will show a 404 page. When not styled properly, users may get confused and get a default 404 WordPress page stating “The page you requested could not be found. Try refining your search, or use the navigation above to locate the post.”

Luckily with a premium theme like Divi you can design and configure a styled 404 page.

If there is no 404 template defined yet, you can do so by clicking on “Ad New Template”.

Next select 404 Page and “Create Template”

Now you can customize the template by adding Custom Body and/or Custom Header/Footer. This works quite similar with designing standard Divi Pages.

Don’t forget to save the changes after changing Body/Header/Footer and for sure hit “Save Changes” when you are back in the Divi Theme Builder.