To configure the web server to show custom error pages for a site or a directory within a site:
error_docs directory in the virtual host directory of the domain, select File in the Type menu and specify the file name in the Location field. error_docs on a domain, select URL in the Type menu and enter the path to your document in the Location field. The path should be relative to the virtual host root (that is, <vhosts>\<domain>\httpdocs).For example, you have created a file forbidden_403_1.html and saved it in the my_errors directory located in the httpdocs. To use this file as an error document, you need to type the following path into the Location field: /my_errors/forbidden_403_1.html.
Note: You can use a connection over FTP or File Manager in the Panel to upload your custom error document to the server. By default, all error documents are stored in the /vhosts/your-domain.com/error_docs/ directory (located in C:\InetPub by default).