         // TBD(hmuller)
         return new Vector.<Object>;
     }
-
-    
-    /**
-     *  Returns a reference to the item renderer currently displayed at the 
-     *  specified cell.  If the requested item renderer is not visible then 
-     *  (each time this method is called) a new item renderer is created.  If 
-     *  the specified is invalid, e.g. if <code>rowIndex == -1</code>, 
-     *  then null is returned.
-     * 
+    
+    /**
+     *  If the requested item renderer is visible, returns a reference to 
+     *  the item renderer currently displayed at the specified cell.  Once the 
+     *  item renderer is no longer visible it is recycled and its properties 
+     *  will be reset.  
+     * 
+     *  <p>If the requested item renderer is not visible then, 
+     *  each time this method is called, a new item renderer is created.  The
+     *  new item renderer is not visible</p>
+     * 
+     *  <p>If the specified column doesn't have an explicit width, then the width
+     *  of this cell will be based on the <code>typicalItem</code>.  If a 
+     *  <code>typicalItem</code> was not specified or hasn't been measured yet, 
+     *  then the item renderer's width will default to <code>150</code>.</p>
+     * 
+     *  <p>If the grid property <code>variableRowHeight</code> is 
+     *  <code>true</code> (the default) and an overall row height hasn't been 
+     *  cached for the specified row, then the item renderer's height is based 
+     *  on the <code>typicalItem</code>.  If the <code>typicalItem</code> wasn't 
+     *  specified or has not been measured yet, then the item renderer's height 
+     *  will default to <code>26</code>.</p>
+     *  
      *  @param rowIndex The 0-based row index of the item renderer's cell.
      *  @param columnIndex The 0-based column index of the item renderer's cell.
-     *  @return The item renderer
+     *  @return The item renderer or null if the cell location is invalid.
      * 
      *  @langversion 3.0
      *  @playerversion Flash 10

        const visibleItemRenderer:IVisualElement = getVisibleItemRenderer(rowIndex, columnIndex);
        if (visibleItemRenderer)
            return visibleItemRenderer;
        // TBD(hmuller): create an item renderer
        return null;
    }
    
    /**

    
    /**
     *  @private
     */
    private function getColumnHeaderBar():ColumnHeaderBar
    {
