用英语介绍Friday the 13th （黑色星期五）的起源

Black friday from Western religion and superstition:Jesus Christ died on Friday,while the number 13 is unlucky.The combination of people believe that the unfortunate things will happen that day.Friday and the number 13 represents the bad luck the last two unfortunate individuals together to form super-sad day.Therefore,no matter what the occasion of the 13th month on Friday called "Black."

http://urbanlegends.about.com/cs/historical/a/friday_the_13th.htm