Net WMNetWM is a set of standards regulating the functionality of window managers under XFree and derivate windowing systems. It is the current de facto standard adopted and recommended by the freedesktop.org* project.
You can read the latest version of the specification here: http://freedesktop.org/Standards/wm-spec
This standard serves to ensure that applications meant to interact with window managers can do so in a consistent manner no matter what particular window manager is used. Another common term for this standard is EWMH (Extended Window Manager Hints).NetWM is the 2nd generation standard, which is currently used by most of the recent releases of popular window managers, including those from KDE and Gnome. The previous one was ICCCM.
Blackbox releases up to and including version 0.65.0 follow the ICCCM standard, while 0.70 and later follow NetWM.