changing background with CSS : I really need your help please guys. I am a completely beginner on this field, and I am stuck with my school project which has to be done in a few days. I've coded a page which has a white background taking the full width of the screen, what I want, is to have the left side and the right side of my page with a grey background, with the background of my content remaining white and pushed a little bit to the centre. Also, the bottom and the top has to remain the same, and as I said, I only need the right and left side to be changed.

To be more specific, the sides with grey background needs to be something like 95pixels width (which is about 2-3 centimetres).  So how do I do that with CSS? [these are my html][2][this is the end of my html although I couldn't screenshot the closing divs][3].

Many thanks in advance


  [1]: https://i.stack.imgur.com/mHYq0.png
  [2]: https://i.stack.imgur.com/jLP1V.png
  [3]: https://i.stack.imgur.com/dCKM4.png