You can design your own error page using html and css, upload it to your website files (htdocs) and use the option in the panel to change error page redirects.
You can refer to this video tutorial related on how you can change error urls: iFastNet - Video Tutorials | How to add custom error pages in Vista Panel
For example the default 404 error of InfinityFree is the following:
404 Page Not Found - InfinityFree