• The stylesheet file references :
  <link ref=’stylesheet’ type=’text/css’ href=’path/to/style.css’ />
• The common selector :
  tag { property: value }
• The group selector :
  tag0,[tag1],[tag2],… { property: value }
• The class selector :
  [tag].class_name { property: value }
• The tag with particular attributes selector :
  tag[attr='value'] { property : value }
• The id selector :
  [tag]#tag_id { property : value }
• The CSS comment :
  /* …… */