May the custome error page be not of HTML format - (asp, php etc.) on LiteHost plan?
Yes, you can set custome error page in asp and php format also .
It requires you set the error page to an URL though, not a file.
At least I assume that’s still the case 
you can set it to a URL like /error_404.asp
thats what i have for one of my websites . then i have a page saying error xxx and sends me an email alerting about the error page
Where do you enter the custom error page address in H-Sphere? I’ve been looking all over.
Nevermind, found it 