http://www.wikihow.com/Sit-at-a-Computer

Your head weighs about 10lbs and if you are tilting you head forwards while using the computer, then that is 10lbs of weight being held by the muscles, tendons etc. in you neck and upper back. So make sure your screen is level with your eye line (top of screen horizontal to eyes).

The desk you sit at (assuming that you are sitting at a desk ) should be at the same height as your belly button (roughly) - this means that your shoulders can be relaxed when using your keyboard and will also decrease the risk of you leaning forward with the resulting head weight issue.

Take regular breaks ( a few seconds every 15 minutes) a few minutes every hour.

There ends todays lesson for healthy computer use. Soup