ServletContext.log messages are sent to the server log. By default, the System.out and System.err output of servlets are sent to the server log. During startup, server log messages are echoed to the System.err output. Also by default, there is no Windows-only console for the System.err output.
You can change these defaults using the Administration Console Write to System Log box. If this box is checked, System.out output is sent to the server log. If it is unchecked, System.out output is sent to the system default location only.