If you are using a PC there is some nasty ransomware and malware stuff out there. There are some that can actually hijack and encrypt your files and then ask for $350 or $500 to unlock them. Fortunately, you are on a Mac (editor’s note: you are on a Mac, right?) and that is not going to happen. But there is an annoying piece of software out there that claims to do something similar.
This software takes advantage of a JavaScript exploit in Safari. Basically, it is a JavaScript popup that presents you with a message that your files and browser are locked unless you pay up. DON’T PAY! There is a much simpler way to deal with this annoyance.
You need to first Force Quit Safari by going to the Apple menu in the upper-left corner of your screen, choose Force Quit, select Safari and hit Return. Then you want to relaunch Safari BUT this time hold down the Shift key as you launch Safari. This will load Safari without loading previous content. We also recommend resetting Safari by going into the Safari menu, selecting Reset Safari, leave all boxes checked and click Reset.