Assignment Q2

 @media (max-width: 720px) {

  #header {

    grid-column: 1 /13;

  }

  #navigation {

    grid-row: 2;

    grid-column: 1 /13;

  }

  #sidebar {

    grid-row: 3/12;

    grid-column: 1 /4;

  }

  #main{

    grid-row: 3 /12 ;

    grid-column: 4/ 13;

  }

  #ads{

    grid-row: 12;

    grid-column: 1/4;

  }

  #footer{

    grid-row: 12;

    grid-column: 4/ 13;

  }

}