is mackeeper a scam or is it legit?

I keep having Mackeeper pop up on my computer and other pop ups when I am in safari, and now firefox. It got so bad with safari that I started using other internet browsers, and now it is happening to firefox. I have deleted internet history and all the cookies with the sites. I am not sure what else to do to fix the problem. Not sure if I should run mackeeper or if it is a part of these pop up issues I have been having.