Text (AN/RV+errata): 6/3. ; Whenever ~this~ attacks, flip a coin. If you lose the flip, remove ~this~ from combat and tap it. [Oracle 1999/09/03]
The coin flip is done as a triggered ability on declaring the Djinn as an attacker. [bethmo 1997/08/08]
Any abilities which have already resolved before the coin flip are not undone. Any abilities that trigger when it attacks which have not already resolved will still resolve. [D'Angelo 2000/02/25]
If Nettling Imp, Siren's Call, or similar effect is used on the Djinn and the coin toss fails, then it still attacked and will not be killed at the end of the turn. [D'Angelo 2000/02/25]
Extended tournaments (see Rule 913) have banned this card since 1999/10/01.