It sounds like a problem with your ISP and/or their DNS server. It will probalby clear up on it's own after a bit. If you have a cellular capable iPad with a data plan, you can turn off wi-fi and use that for a while.
But here are some other things you can try in the mean time, because they might help.
Go to Settings > Safari and Clear Cookies and Data. You'll have to sign back into any websites that normally remember you.
Restart both the iPad and your router. When they boot again any old setting will get refreshed from the ISP, possibly fixing something.
Good luck.