This article describes how to create a customer error page in DotNetPanel.
1) Once logged into DNP, goto Web Sites and select the domain in question.
2) Click on the Custom Errors tab
3) Enter the error code for example: 404
4) Select Execute URL as the Handler Type in the dropdown list.
5) Enter the page to redirect to under Error Content, make sure to enter slash before your page ie: /404.asp
6) Click the Update button, to update your website to now have a 404 custom error page.