The Card Key is found on the floor of the fifth floor of the Silph Co. building in Saffron City.
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If you want to get the card key, you must use the elevator and go to 5th floor. Then done.
You can find the Lift Key in the Team Rocket Hideout on Pokemon FireRed. It is dropped by a Grunt on basement floor 4 after defeating him.
Last time I heard, you have to go to a Nintendo Event.
You find it on B4F in FireRed when you battle a Team Rocket Grunt in the far north corner he has a Level 21 Zubat and Koffing, if you defeat him, then he will drop the key. This will enable you to battle Giovanni. In Silph Co., you don't need a lift key to get anywhere, instead, you have to use the teleporters to get to the Card Key.
The card key in Pokemon Heartgold and Soulsilver is located in the Goldenrod Underground.