Pop-ups

I have a 2012 Macbook Pro. Recently, I appear to have downloaded or otherwise obtained something that causes two problems. First, I have double underlined green links have little pop-up flag adds when scrolled over. I opted out of these, but apparently that just installed a cookie that blocks them and doesn't get rid of the underlying cause. If possible, I want to get rid of the problem. Second, I am getting pop-up adds all over. Wikipedia and Youtube are especially bad, with addblocker blocking 1000+ adds in about 10 minutes (addblocker doesn't catch all of the adds, either). What can I do to get rid of whatever it is that is causing the problem?

*I use Chrome, but the problems are identical in Safari and Firefox.