How do I Stop objects from falling through the floor?

Everytime I start my game, the objects in the game fall through the floor it there a way to stop the from falling through the floor and just stay stood on it?

We have know way of answering that without more information and possibly your .capx.

Have you looked at the built-in examples/templates?

Have you done any of the excellent tutorials?

How have you setup your level?

What behaviors are you using?

What type of game are you making?

I've made the floor and solid and the crates solid so shouldn't the crates just stay sat onto of the floor?

Well, no that's not enough. After you make both of them solid you have to tell C2 what happens when the respective solid objects collide with each other.

I suggest you read/do this tutorial. It adresses your question and teaches you other useful things too.

FlameFoxx Does your crates have any physics behavior? That usually makes them fall through solid objects.

They do. Anonnymitet, thats just so they topple when the cannonball or anything else hits it.