[newbie] Logger Appender

[bagas]

Hi all,
 
I try to use log4j as httpclient logger but I receive a warning :
 
log4j:WARN No appenders could be found for logger
(org.apache.commons.httpclient.HttpClient).
log4j:WARN Please initialize the log4j system properly.
 
How can set an appender to a logger ? please give me a example
 
Thanx