I am getting inundated with pop-up ads
I am getting inundated with pop-up ads, web pages being replaced with some type of product page (and not n a new tab, replacing the page I am on such as weather.com) and the intended page I am on not working properly such as the back button not working because there is something from pop ups or another page running in the background. Any suggestions to clean this up? What is happening and how do I make it stop.
MacBook Air (13-inch Mid 2013), OS X Mavericks (10.9)