The path for the base filename of the cascading stylesheets for the site. Commerce Reference Store sets this property to:

The value for this property is not a fully qualified pathname. Commerce Reference Store includes additional logic for resolving the full pathname when it uses this property. See Cascading Stylesheets (CSS) for more information.

If the cssFile property is not set for a site, Commerce Reference Store uses the /atg/store/StoreConfiguration component’s defaultCssFile property instead. This property is set to /css/site/store in Commerce Reference Store.