Operation of a Laptop in awkward positions, commonly leads to neck pain, back pain and mal-alignment of the spine, especially in children. These positions include: lying on your stomach, leaning back on the arm rest of a couch and lying on your side etc. It is very important to maintain proper posture when using a laptop, to avoid injury and general pain associated.
For brief usage of a laptop, make sure that you are seated in a chair with proper back support. Place the laptop on your lap or on a stand. Make sure the angle of the screen is adjusted so viewing is optimal while maintaining good posture.
Long term usage
While using a laptop for work or for a prolonged period of time, it is best to convert the laptop into a desktop. Place the laptop on a desk surface and adjust the height of the laptop, either with books or with a stand. The top of the screen should be just under eye level. Do not use the trackpad and keyboard associated with the laptop, instead attach an external mouse and keyboard (preferably ergonomic).