It's not an operating system, because it cannot operate the system  (your system being the Computer) :) Sorry for the obvious fact, but that is.<p>For example Linux, Mac OS X, Windows do control your System by taking over all resources, interrupts, almost anything.<p>At best this is a Browser Operation System (BOS), and even then it's not - because it does not have control over the Browser.<p>It's an illusion.