59th rankedPhil Coulomb commented
I posted this, Since that time have found on my device a firewall additional app that has engaged itself. The app is hot spot protection and it was limiting my Internet data so when a set limit was reached for some reason Yahoo was being targeted. I have turned it off and found settings to prevent it from turning on automatically. So far no more ERROR code 100 site unavailabe notices. Hope this was it.l
On the web others have suggested deleting AD Block history and clearing web History and Cookies.