I believe that it is perfectly fine to surf for pleasure during working hours if it is done under responsibility. You still have to perform your work tasks satisfactorily, but if you have some idle time to spare or need a break, it should always be perfectly acceptable to surf for pleasure for a short while during working hours.
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You are entitled to a 5-minute break every hour, so if the employee chooses to, for example, surf around a bit, then I see nothing wrong with that!