Interpretation of Java or Ruby neccessary with every access?
Java is compiled to bytecode, and then (usually) compiled to machine code using a Just-In-Time  (JIT) compiler.  Java servers don't launch a new process for every request (most just launch a new thread), so the cost of the JIT compile is amortized across the entire lifetime of your server.  In practice, this means that Java servers can handle requests at speeds comparable to C or C++ (modulo the different performance profile of automatic memory management).
Python is compiled to bytecode, but the bytecode is interpreted each time it is executed, much like PHP with a bytecode cache.  There has been some work on JIT compilers for Python (Psyco was one, and PyPy has done a lot of work with JITs) but they aren't generally considered production-ready.  (YMMV, of course.)
JavaScript on the server can be interpreted to mashine code using Google's V8 Javascript Engine. But PHP and Ruby and Python and Java all have to run through an interpreter every time they're accessed and it interpretation will be less fast.
Is that true? I read this in an article about Google's V8 Javascript Engine.