Knowing the order of what's being called is very important when coding in Flash. For example, you might create a call in a component's inspectable attribute, like this

[Inspectable(type=Number, defaultValue=400)]
public function set width(w:Number)
{
__width = w;
child.refresh();
}

You might need think your child.refresh will get call, when in fact at instantiation time, your child won't be called because when width was set, child has not been instantiated yet. So you must call child.refresh( ) in your onLoad function.