Why does a cake flop?

Answer 1

Could be:

1) Not enough air in it. You must beat the cake mixture well when mixing margarine, eggs and butter. Then be very careful when you add the flour. It's a good idea to seive flour before adding it to get more air in it. Just gently fold the flour in with a metal spoon.

2) Oven might not be hot enough. Be sure to heat the oven to required temperature before putting cake in to bake.

3)Opening and closing oven door during baking. If you do have to open it do it very gently.