Apple Users

Is DIY a web hosting service? Free or paid? If you're sending them $ then they should respond to requests for help.

But offhand it sounds like a connectivity issue rather than an issue with your HTML code.

Hard to guess what's going wrong, but ... some random q's to start off with ...

1) did you set up a domain name for the host or are you connecting to an IP address?
2) if a hostname, does DNS resolve to the right address? (vs. a problem/error with the name lookup)
3) if an IP address, does the address you're using really match the IP address of the computer that hosts it?
4) is it behind http or https?
5) if http, a lot of browsers are defaulting to https, so you might need "http://www.mydyihost.com" instead
of just "mydyihost.com"
6) if https, perhaps your security certificate may have expired
7) are the iPads and the iMac using the same domain-name servers?

Interesting puzzle