Paraskavedekatriaphobia is the fear of Friday the 13th. Youcan read some interesting things about Friday the 13th on wikipedia http://en.wikipedia.org/wiki/Friday_13
I was surprised to read that it is a relatively new superstition - although some claim it has ancient roots. One of the reasons given is that 12 is the number of completion: 12 months, 12 tribes of Israel, 12 disciples of Jesus. That makes 13 irregular and "transgressing this completeness". Interesting. Oh, and that at the last super there were thirteen present (on a Friday) so one had to die.
Wellllll, what should a Christian's response be to Friday the 13th? (By the way, there is only one this year, but three next year.) There is no place in the life of a Christian for superstition or fear of these kinds of things.
1 John 4:4 You are from God, little children, and you have conquered them, because the One who is in you is greater than the one who is in the world. Study This Chapter
A Christian should not fear black cats, should not "knock on wood" or any of those kinds of things, because we are children of God! Our lives should be lived in such a way that people know we have a hope and a future Jer 29:11 because we have been redeemed and have the Spirit of God living in us Ro 8:9 .
So go out and do something great for Christ today. Use Friday the 13th as a chance to explain to others the peace and joy and hope you have as a follower of Jesus Christ!