password

I changed my yahoo password on computer and my ipad will not accept it, yet my iphone did.
Also wont accept my apple id.

Changing your Yahoo account password should only affect your Yahoo account and Yahoo email. It wouldn't affect your Apple ID. I have read on this forum that it is a major hassle to change your current Apple ID...except for maybe the password in case the account was hacked. It is better to just create a new Apple account, but things purchased and downloaded on the old account would have to be purchased and downloaded with the new Apple ID account. I hope I have this right.

It's not difficult to change anything about an Apple ID except the name it was originally set up as. That cannot be changed at present.

As you observed, the OP's first question doesn't really have anything to do with his second issue.

For the Yahoo problem, try signing completely out of the Yahoo site or application on your computer and then signing back in. That will verify that the problem is specific to your iPad.

Second, try shutting down the iPad -- not just putting it to sleep, completely powering it down and then turning it back on again. Now try to sign into the Yahoo application.