There's malware going around that locks people's browsers, claiming that their computer (or other device, such as an iPad) has been used for illegal activity and demanding payment of a 'fine' in order to settle the matter and unlock the browser. If users attempt to use (or close) their browser they get a message that it has been blocked (or locked) 'for safety reasons'. I suspect that something similar may have found its way onto your iPad.
Sorry, we can't find any related questions. Try using the search bar at the top of the page to search for some keywords, or choose a topic and submit your own question.