http://java.sun.com/j2se/1.4.2/docs/guide/plugin/developer_guide/tracing_logging.html

According to the end part of the above page,
when we specify the property
  javaplugin.outputfiles.overwrite=false
we can get the trace file and log file as the following name.

.plugin<username><date hash code>.trace and .plugin<username><date hash code>.log

In other words, we hope the trace and log information for each session
respectively.
However, even when we set javaplugin.outputfiles.overwrite=false ,
We still get the
    .plugin<version>.trace and .plugin<version>.log
under the F:\Documents and Settings\<user>\Application Data\Sun\Java\Deployment\log

REPRODUCE :
    1) Open the java control panel in [start]-[control panel]
    2) click the tab [java] and open the setting runtime.
    3) Specify the properties as follows.
        -Djavaplugin.trace=true -Djavaplugin.trace.option=basic|net|security|
ext|liveconnect -Djavaplugin.logging=true -Djavaplugin.outputfiles.overwrite=false

    4) Look at the F:\Documents and Settings\<user>\Application Data\Sun\Java\Deployment\log
       The trace file and log file name is
         .plugin<version>.trace and .plugin<version>.log

EXPECT :
   We can getthe trace and log files in
    .plugin<username><date hash code>.trace and .plugin<username><date hash code>.log
   as the web page expains.

ACTUAL :
    plugin<version>.trace and plugin<version>.log

CONFIGURATION:
   OS : WIndowsXP(SP2, Japanese)
  JRE : 1.5.0-beta3-b56
  Browser : IE 6.0 (SP1)

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