Why is 13 considered an unlucky number?

Poor number 13. People have been uneasy about it since primitive man counted his ten fingers and two feet and came up with 12. After that came the unknown--13. And anything unknown is scary. As with all superstitions, there is no reasonable answer. But that doesn't mean people don't take it seriously. Many hotels and office buildings don't have a 13th floor!

HAHA! WTH