The information below has been taken from the AYSO Basic Referee course materials, and contains the information that is presented in every 6 hour course. This could be helpful as a review or to print out and study before you take the test at the end of the class. These cannot be used in place of taking the course from a certified instructor.
Explanation of the Offside law The link below is to a clip that gives an excellent presentation of the offside rule.
It has one error in that it states "when the ball is kicked"....instead it should state "when the ball is played" because a player can be in violation of the offside law if a player heads it to him/her or even if it accidentally bounces off a teammate, not just when it is kicked click here for video cilp