For many of you, this issue is due to some security vulnerabilities in Android. The exploiters are using a built in popup feature in Chrome to display all these "warning" pages which aren't legitimate warnings at all - they want you to click their links, so that they can install even more malware onto your phone.
The quickest way to address this, and still keep all your login and cached data, is to go into your Android's file manager, look for a folder called "GoAdSDK" and delete it; then, do a full shut down/restart on your phone. This android ad-based malware is very tenacious, so don't be surprised if it comes back.
Installing an ad blocker/firewall like DroidWall will also help.
If you are experiencing this issue on an Apple device, then it would be good to know if you are seeing it using the Chrome browser, or Safari? If you are using Chrome, then the solution for you is the same as above- Go find the GoAdSDK folder, and blow it away
Last edited by moore_rb; 12-16-2016 at 08:03 AM..