And you should be - cyclingfans and steephill connect to some "free" tv sites that sometimes have pop-ups that you should never click on 'cause if you do, they will either try to sell you stuff you don't need or get your computer infected and not just windows but macs too I warrant.
However, with the right pop-up blockers like uBlock Origin and one or two other tools plus some common sense, you can defeat this stuff. It's just not easy for the novice, let along experienced user. You have to know a little bit about what to do.