Zero reduction in productivity

They call it cyber-slacking, sure if you have a heavy workload and neglecting it by constant non-work related browsing halting your productivity I guess you can be called a cyber slacker but if you have very little or near zero workload and you spend your time at the office browsing after you have finished the work you wouldn't be slacking now would you? since going home early isn't an option when working in an office environment what else can you do but surf teh eent4rw3bz?