I need to know how to get rid of viruses

Recently my Macbook Pro has been redirecting me to a page where I have to install something called "Lightspark Player Pro". I didn't click on anything, I was just using Google Docs and it keeps taking me to that page. I just force quit safari and reopened it but it keeps taking me to the page. It only does this when I am on certain websites but it happens a lot (I have also installed Firefox, Genio (I keep deleting and and it just magically reappers), and Dropbox). It doesn't do this on Firefox though. I really need to fix this, I have searched through the forums and avoided everything that people say has viruses, like Mackeeper, but still I haven't found anything that clears my viruses. Are there certain websites I should avoid? Things I shouldn't download? Everything helps. I can always rely on you guys to help solve my problems very fast. 🙂