Localization of validation messagges and their css

[Otho]

Hi all,
is there a better/more standard way to localize validation errors than to
create org.apache.tapestry.internal.ValidationMessages_xx_XX.properties and
org.apache.tapestry.corelib.components.Errors_xx_XX.properties in resources
package? And where do I override the css?
Regards,
Otho