It's something that happens to everyone: you're checking your e-mail and a message catches your eye. It says it's urgent and it seems to come from a company or person you think you know, so you open the message. It tells you there's a problem with your account and to use a link provided in the message to fix the problem. If you click it, it goes to a page that looks right, but how can you really be sure? How do you tell which e-mails are safe and legitimate from the ones that are looking to steal your information or, worse, money?