I got this information from my doctor, he told me that, who use their laptops on the floor, in bed or on their laps are likely to develop injuries in their neck, shoulders and wrists.
If we use laptop in wrong direction or wrong way it will cause our body.That is hand and arm pain due to repetitive strain injury , which is induced by resting wrists against the edge of a laptop.
Choose a laptop with as large and clear a screen as possible(14" diagonal or more). Make sure the laptop is stable and will not wobble or slide as you work,rest your eyes frequently and blink more to prevent them feeling dry,
And also we should sit with the laptop centrally alinged with body with wrists in line with forearms, shoulders relaxed and back supported.