moving thread to RichFaces space from RF development
if you will not define level - it will depends on your user agent version. If defined basic - stylesheets for IE 7/8 and FF of latest versions will not be loaded. Only compatible with older browsers ones will be loaded. If extended selected both stylesheets will be loaded for these browsers and skipped for IE6 and so on. Consider note that IE 6 not supports many properties of standard skinning selectors.