Exerciers.mobi site is known for displaying the multitude of extremely annoying pop-ups through all popular browsers today, such as Google Chrome and Mozilla Firefox.
Exerciers.mobi pop-ups are dangerous because they may start showing various unwanted push notifications if you allow these notifications to be enabled.
Here is the guide that may help you fix this issue - https://trojan-killer.net/exerciers-mobi-push-notifications-removal-solution/
Video guide on how to remove this infection with GridinSoft Anti-Malware -
Download removal tool here - https://anti-malware.gridinsoft.com/download