Why is there a new "blue moon" today and how did the No. 13 become to be an unlucky number?

Is today an off-day for our universe? Nov. 21st and a second full “blue moon” this month? Does this mean we will have another full moon on Dec. 21, 2010? Question: How did the number 13 become an unlucky number for some of us? Is 13 tied to number of full moons earth will have this year, instead of 12?

Source: Space.com