code: function contentHeight( scrollable )
  	{
  		var overflowY = scrollable.getStyle( 'overflow-y' );
  
  		var doc = scrollable.getDocument();
  		// Create a temporary marker element.
  		var marker = CKEDITOR.dom.element.createFromHtml( '<span style="margin:0;padding:0;border:0;clear:both;width:1px;height:1px;display:block;">' + ( CKEDITOR.env.webkit ? '&nbsp;' : '' ) + '</span>', doc );
  		doc[ CKEDITOR.env.ie? 'getBody' : 'getDocumentElement']().append( marker );
  
  		var height = marker.getDocumentPosition( doc ).y + marker.$.offsetHeight;
  		marker.remove();
  		scrollable.setStyle( 'overflow-y', overflowY );
  		return height;
  	}
docs: Actual content height, figured out by appending check the last element's document position.