That’s just a JavaScript scam. It can’t hurt you. You can even click the OK button and it’s not going to do anything. Do that, then close all Safari tabs/windows once the alert has been dismissed.
Next, check your home page setting in Safari -> Preferences -> General -> Homepage. The page that is causing that message to appear is goggle [dot] com – note the misspelling. If you have set your home page accidentally to this site, change it to the proper spelling of Google.
(zdroj: diskusia na Apple Support Forum)