Nowadays people spend too much time in front of the TV , computer screens and mobile phone. Over time can cause problems for our health. I don't use too much the computer but i recognize that i use constant the mobile phone.
Using too much these tecnologies is harmful to our health, especially can cause eye problems and maybe you have to wear glasses that it's my case. Another problem is that the position is not good and cause neck and back problems. Also can cause addiction and stop doing other things, for example, children can suffer obesity because if they spend too much time in front of the tv or computer became sedentary and they don't do exercise.
In summary, if you use these technologies in moderation is not harmful , without downplaying outdoor activities so you don't become sedentary.