New To Java - Help P-L-E-A-S-E

Okay, I have no clue about java period. just starting to learn, one of our servers at work is giving me a Java.Lang Unsupportedclassverion error. This was dropped in my and I really have not a clue to what is causing this error.
[235 byte] By [LOst001a] at [2007-11-26 23:26:28]
# 1
You compile it in a later version which run in a earlier version of JVM ?
rym82a at 2007-7-10 14:34:31 > top of Java-index,Java Essentials,New To Java...
# 2
I am not sure, it was already setup when I was put in charge of that server. But the verision is 4.1
LOst001a at 2007-7-10 14:34:31 > top of Java-index,Java Essentials,New To Java...
# 3
Do you have the station which you compile the source code ?If you do, type java -version on both the stations you compile and run.
rym82a at 2007-7-10 14:34:31 > top of Java-index,Java Essentials,New To Java...