Nistelrooy was not offside after all

Premier League referees' chief Keith Hackett said that the goal Van Nistelrooy scored was okay after all.He looked a mile offside when he knocked the ball past Buffon.
But it appears he was played onside by defender Christian Panucci, who was lying off the pitch at the time.Take a look at the picture.You can see him lying there.
"The fact is the assistant was correct; the defender who slid off the field is still regarded as active," Hackett told BBC Sport.
"Christian Panucci went off through contact with his own goalkeeper.He is still considered part of the game." This apparently is the correct interpretation of the offside law - rule 11
So there it is folks.You learn something every day.