Little tip in case ou want to have HIGHER level of logging from tomcat (version 5.5 or higher), because he fails to do something but just says failure ;-)
Tomcat, out of the box, does not include any logging library. However, if you want to make some fine-tuning on the logging, he is ready to achieve your configuration.
At startup (my guess...) Tomcat checks if some special configuration has to be applied, via the "bridge" interface commons logging . This library can be described as a logging implementation abstraction layer. If so, he applies it. Commons logging interface hides the actual implementation, that is, you can use either log4j or any alternative behind the scenes.
Anyway, drop the commons logging and log4j jar files in the common/lib directory, write a file in the common/classes directory, and you should be fine. example :

log4j.rootLogger=ERROR, A1

# Print the date in ISO 8601 format
log4j.appender.A1.layout.ConversionPattern=%d %t %-5p %c - %m%n

Pour tester tout ça, rapatriez ce petit projet JSF dans eclipse, ant compile et deploy...