The javadoc page for the PatternLayout class (http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/PatternLayout.html) uses "it's" instead of "its" everywhere.
Changes committed in Java source in rev 746253 for extras and 746254 for log4j 1.2. Online Javadocs will be updated when 1.2.16 is released.