Colin Natali emphasised on maintaining a good posture while sitting, which can be obtained by getting an ergonomic chair or assessment which generally looks at the seat height, elbow angle and armrest height.
It is vital to also look into the Low back support. Natali has suggested pushing the bottom against the back of the chair, which will help preventing pelvis from rotating backwards. There may be a lumbar support inbuilt in the chair, if not, a cushion will help maintain the curve of the spine and prevent the person from slumping.
Eye level is also one important consideration, which should be kept in mind. The head should be held upright to follow the curve of the spine. This is important as the average human head weighs between 10 to 12 pounds.
However, if a person is constantly bending his head forward to look down at the screen, then he can be exerting as much as 30 pounds of pressure on his neck and upper spine. This will minimise the likelihood of neck pain.
Finally, no matter how comfortable a person is in his chair, prolonged sitting in front of your computer is not good for the spine generally and is a well-known cause for neck and back problems.
Article source: http://www.medindia.net/news/Steps-to-Prevent-Backaches-in-Office-92449-1.htm