It's a parent's worst nightmare - a child becoming the prey of a sexual offender. Unfortunately, the sick individuals who stalk young children aren't branded with a scarlet letter, and by the time some parents find out that a predator has infiltrated their surroundings, it's too late. In the United States, a child goes missing every 40 seconds. And although 90 percent of all molestations are done by someone the child knows, at least 10 percent of the crimes are committed by strangers. It's a frightening statistic, but there are preventative measures that can be taken to keep your child out of harm's way.{relatedarticles} In the age of the information superhighway, there are Web sites that show where registered sex offenders live. In many states, you can go to state-operated Web sites and input your address. The sites then provide you with the addresses of the offenders, along with information of their crimes and their photos.