Why all the fear of Friday the 13th?
In France, on (Friday) October 13, 1307, King Philippe IV attacked the Knights Templar. All the Templars in France were arrested, accused of heretical acts, imprisoned, tortued, and executed. The day forever branded Friday the 13th as an unlucky day.
An interesting little fact (found in Seventh House's Season of the Witch planner) The greatest number of Friday the Thirteenths that can occur in one year is three, and that is the case in 2009: Feb 13, March 13, Nov 13.