Happy Friday the 13th, triskaidekaphobes!
Actually, there is a specific word meaning "morbid, irrational fear of Friday the 13th" -- paraskevidekatriaphobia:
The sixth day of the week and the number 13 both have foreboding reputations said to date from ancient times. It seems their inevitable conjunction from one to three times a year (there will be three such occurrences in 2012) portends more misfortune than some credulous minds can bear. According to some sources it's the most widespread superstition in the United States today. Some people refuse to go to work on Friday the 13th; some won't eat in restaurants; many wouldn't think of setting a wedding on the date.
You wouldn't believe all the things it's supposed to be unlucky to do on Friday the 13th. Blog posting isn't one of them; I looked it up. Hey, credulous minds want to know!