Read pop-up windows closely. Don’t just click OK to close pop-up windows as fast as possible. Clicking the “OKâ€ button could be dangerous. It could allow some Active X component or Java applet to run on your system and install whatever. These can be good or harmful to your computer. “It is all about using common sense when you are doing stuff online,â€ says Cargill. “You really need to read that message. Sometimes they try to get tricky with the pop up windows. If you hit cancel it might still install the virus.â€ Instead hit the Esc (escape) button on your keyboard. Esc will close the window no matter what they’ve done with Java script to cover up the buttons.