title: web page with 3 different colors, 1cm margins, not getting desired results
body: <p>I want to divide my web page into 3 divs, with 3 different colors, When I use <code>width:100%</code>, 1 centimetre of margins are empty and have not that color. </p>
  
  <p>What should I do to fix this problem?</p>
  
  <p>Example of the problem:</p>
  
  <p><img src="https://i.stack.imgur.com/XJvNG.jpg" alt="enter image description here"></p>
  
  <p>Fix sample</p>
  
  <p><img src="https://i.stack.imgur.com/3z8yO.jpg" alt="enter image description here"></p>