fx:Binding must be a child of the root tag.

‘<fx:Binding>’ must be a child of the root tag.

Cause
The tag cannot be nested more than one level deep.

Incorrect:

<s:Group xmlns:fx="http://ns.adobe.com/mxml/2009" 
		 xmlns:s="library://ns.adobe.com/flex/spark" 
		 xmlns:mx="library://ns.adobe.com/flex/mx">
	
	<fx:Declarations>
		<fx:Binding source="EffectManager.mx_internal.activeEffects" destination="effectsArray"/>
		<fx:Array id="effectsArray" />
	</fx:Declarations> 
</s:Group>

Correct:

<s:Group xmlns:fx="http://ns.adobe.com/mxml/2009" 
		 xmlns:s="library://ns.adobe.com/flex/spark" 
		 xmlns:mx="library://ns.adobe.com/flex/mx">
	
	<fx:Binding source="EffectManager.mx_internal.activeEffects" destination="effectsArray"/>

	<fx:Declarations>
		<fx:Array id="effectsArray" />
	</fx:Declarations> 
</s:Group>