How can I prevent from inappropriate ADS pop up randomly on my screen?

[Android Central Question]

Let me be more clear. I don't know what I've download. But this has happened since ever I downloaded an app. it's the first time. So, these ADS are popping out of nowhere on my screen, it doesn't matter what app I'm using( well the games doesn't matter) And i know the apps that I use they don't have ads...... the ads that are coming out randomly are pornography, the most. ?How can I remove them? Because I don't want one day my friends,to unlock my phone and see that I watch porn! which I don't.

 

[belodion]

Settings, Apps, All, the offending app, Clear Cache, Clear Data, Force Stop, Uninstall.