virus - How can I safely close this window and forever avoid seeing similar pop-ups from Mackeeper Zeobit's malware and spyware?

The attached image shows a window that just popped up and the only button available is the OK button. I could Force quit Safari, but I've got several sites open right now and don't want to try and find my place again. Besides, I've seen similar hacks in the past and I'd like to learn how to handle them in a way better than just a brute force-quit.

I've never heard of MacKeeper or Zeobit, so I opened Firefox and did a few searches while Safari is obviously still stuck, waiting for me to click the sneaky OK button in the dialog window. Anyhow, at least the first few pages of most search results contain lots of blabbering from questionable witnesses about how MacKeeper saved them from some malware or spyware. However, any company that is hacking the browser to maliciously install their product is itself the criminal and not providing a true security application. So, there are three questions here:

1. How can I close this window?


2. Can I do something to Safari to
   
   avoid these hacks in the future?


3. (Just curious) Is MacKeeper or
   Zeobit somehow loading the search
   results so that no information about
   their application being malware or
   spyware is listed (I can't be the
   only person in the world that is
   offended by their tactics, even
   though it appears I am)?