Can I display my error when the site is unavailable?

Question

Domain Name System

Instead:

Let's say a company phone number or a link to an alternative site.
It is possible with perversions of DNS, WebCache, manifest

Answer 1

No

Answer 2

This error is thrown by the browser, not your site.
You can only override the errors that your web server throws.
For example, "invalid page", when you try to go to a URL that is not registered with you.
But the timeout means that your server is not responding, how can it give any error at all? It's already on the client side.
Here are the errors that can be overridden from the server side:
400 Bad Request
401 Authorization Required
403 Forbidden
404 Not Found
500 Internal Server Error

Answer 3

You can't cover this error. Because this error occurs when your site cannot be contacted.
In general, you need to define errordocument on your virthost;)