Unlucky number 13

Not to be confused with Friday the 13th (which is a superstition of the actual day) but similar in nature this superstition simply states that the number 13 is associated with bad luck. Thats why many architects refused (some still do) to design stairs that ended with 13 steps or buildings that ended with a 13th floor. The fear of the number 13 is so real to many people that an actual phobia has been created to describe it; its called Triskaidekaphobia. (try to say that 13 times fast).