title: How to filter by attributes in layered navigation Magento?
body: <p>I have two attributes in my Admin: Color and Size.</p>
  
  <p>This attributes haves this configuration:</p>
  
  <p>Scope: global
  Catalog input type: Drop down
  Apply To: all 
  Use in layered navigation: Filterable with results</p>
  
  <p>And I have configurable products that haves simple products. For example:</p>
  
  <p>CONFIGURABLE: MY T-SHIRT 
  SIMPLE 1: MY T-SHIRT with Color = White and Size = L
  SIMPLE 2: MY T-SHIRT with Color = Black and Size = L</p>
  
  <p>CONFIGURABLE: MY OTHER T-SHIRT 
  SIMPLE 1: MY OTHER T-SHIRT with Color = White and Size = S
  SIMPLE 2: MY OTHER T-SHIRT with Color = Black and Size = M</p>
  
  <p>But I cant't see filter by "Color" or "Size" in layered navigation. I just can filter by price and subcategories.</p>
  
  <p>Why are those attributes not appearing in my layered navigation?</p>