when width css code example

Example 1: width css

/*Based on viewport*/
width: 100vh;
width: 100vw;

Example 2: css width percentage

<div style="background-color:navy;">
  <div style="width:50%; margin-left:20%; background-color:chartreuse;">
    Width: 50%, Left margin: 20%
  </div>
  <div style="width:30%; margin-left:60%; background-color:pink;">
    Width: 30%, Left margin: 10%
  </div>
</div>