Football Players Then And Now

Players are cautioned with a yellow card, and sent off with a red card. These colours were first introduced at the 1970 FIFA World Cup and used consistently since.
A foul occurs when a player commits an offence listed in the Laws of the Game while the ball is in play. The offences that constitute a foul are listed in Law 12. Handling the ball deliberately, tripping an opponent, or pushing an opponent, are examples of "penal fouls", punishable by a direct free kick or penalty kick depending on where the offence occurred. Other fouls are punishable by an indirect free kick. The referee may punish a player or substitute's misconduct by a caution (yellow card) or sending-off (red card). A second yellow card at the same game leads to a red card, and therefore to a sending-off. A player given a yellow card is said to have been "booked", the referee writing the player's name in his official notebook. If a player has been sent off, no substitute can be brought on in their place. Misconduct may occur at any time, and while the offences that constitute misconduct are listed, the definitions are broad. In particular, the offence of "unsporting behaviour" may be used to deal with most events that violate the spirit of the game, even if they are not listed as specific offences. A referee can show a yellow or red card to a player, substitute or substituted player. Non-players such as managers and support staff cannot be shown the yellow or red card, but may be expelled from the technical area if they fail to conduct themselves in a responsible manner.
Rather than stopping play, the referee may allow play to continue if doing so will benefit the team against which an offence has been committed. This is known as "playing an advantage". The referee may "call back" play and penalise the original offence if the anticipated advantage does not ensue within a short period, typically taken to be four to five seconds. Even if an offence is not penalised due to advantage being played, the offender may still be sanctioned for misconduct at the next stoppage of play.