Probably you have an adware on your machine. Download and run AdwCleaner, reset settings in all your web-browsers, delete unused and suspicious browsers add-ons. I would suggest following the complete pop-up ads removal tutorial.
If you’re seeing unwanted pop-ups or ads in your web-browser, you might have an adware installed on your computer. Use the following guide to stop pop-up ads and remove malicious software. Or ask for help here.