I do not know much about soccer, but I copied these clauses from another fan and I think it makes sense especially when u have the rules laid.
It is not an offence in itself to be in an offside position. A player is in an offside position if: • he is nearer to his opponents’ goal line than both the ball and the second last opponent. A player is not in an offside position if • he is in his own half of the field of play or • he is level with the second last opponent or • he is level with the last two opponents. A player in an offside position is only penalised if, at the moment the ball touches or is played by one of his team, he is, in the opinion of the referee, involved in active play by: • interfering with play or • interfering with an opponent or • gaining an advantage by being in that position.
This is what the rule says, and this is all the rule says. (http://www.fifa.com/en/laws/Laws11_01.htm)