In unity go to File >> Build settings.
A new window will pop up. Just hit add current to add you’re current scene. You also can drag your scenes from your project folder. Then they’re appear numbers next to the name of your scene. In your script use this instead:
function OnCollisionEnter (myCollision : Collision)
{
if(myCollision.gameObject.name == "Floor")
{
Application.LoadLevel(// The number next to the scene in the build settings window);
}
}