Q:

Applet jar generated with JDK 1.6 compiler on a system with JRE 1.5

Can a applet compiled with JDK 1.6(but not using any new features of 1.6) work on systems having JRE 1.5?

A:

If the code was compiled using compiler flag -target 1.6 (which is default for 1.6 JDK) - then it will not run on 1.5 JRE. 
However, if the flag -target 1.5 was used - then it will work properly on 1.5 JRE.

