Triskaidekaphobia - the fear of the number 13. It's the reason why so many buildings don't have a thirteenth floor.
No one knows the origins of the phobia for sure. It could date as far back as the Last Supper, when Judas was the thirteenth guest at the table.
If you are a triskaidekaphobe, you're in good company. The AP reports that Henry Ford, Napoleon and FDR all suffered from it. Fortunately for them, they didn't have to endure 2009 - which has had three Friday the thirteenths - the most possible in any given year.
But despite the slasher films by the same name, there is little evidence that today is any more dangerous than any other day. In fact, a Dutch research firm found that accidents decrease on Friday the thirteenth.
That's probably because all the triskaidekaphobes are home - hiding out until Saturday the 14th rolls around.
That's a page from my notebook.
I'm Katie Couric, CBS News.