I'll just let Digital Journal explain:
"After reviewing a promotional video that aired during last Wednesday's episode of America's Got Talent, it's now clear that someone forgot to clear their Internet history.
The video was promoting a $1 million competition, whereby viewers can film their specific talents (in under 90 seconds) and upload them to YouTube.
It's now clear that a member of staff, who remains unknown, has a talent of their own. This became apparent when instructions of how to access YouTube were included in the video.
As YouTube's web address was entered into the address bar at the top of the screen, a list of similar, recently viewed websites was shown underneath. To the shock of viewers who were quick enough to notice the mishap, YouPorn appeared as part of the Internet history."