Hi. In response to your question.....Does this person know that information (or whatever it is that you found) is on the internet? If they don't then i would suggest you privately inform them about it. Im sure they would rather only one person know about the issue than millions. If they do know that it's online (and they are a close friend) then i would confront them about it. It may embarrass them at the moment, but if you are a christian you should always stand for what you believe. If it's something that goes against your beliefs you should express to your friend the consequences of whatever it is that they are doing. I take it that since it is something you feel uncomfortable about it..that what you found is sinful. Remember not to judge them though. Your friend(whether christian or not) needs to understand that it is a sin and if they don't change whatever it is...the consequence is hell. Its hard to explain what you should do without knowing what the issue is..but i hope that something i have said will make sense. Good luck and God Bless.