Help Your Server to Find the 404 Page
To tell your web server to use your custom error files, you’ll need to edit the .htaccess file in the main directory (where main index.php file resides) of your WordPress installation.
To ensure the server finds your 404 page, add the following line to your
The url /index.php is root-relative, which means that the forward slash begins with the root folder of your site. If WordPress is in a subfolder or subdirectory of your site’s root folder named ‘wordpress’, the line you add to your .htaccess file might be: