In a large bowl, mix together the pudding mixes, Cool Whip, and milk.
In a 9 x 13 inch pan, place a single layer of graham crackers on the bottom of the pan (you may need to break a few graham crackers so that the entire bottom of the pan is covered).
Spread half of the pudding mixture evenly over the graham crackers. Place another single layer of graham crackers on top of the pudding and then layer the second half of the pudding on top of those crackers.
Place one more single layer of graham crackers on top of the pudding.
Mix together ingredients for the lemon frosting and spread over all.
Cover and place in the fridge for about 4 hours.
Notes
We found that we like this cake even better then next day.