The Tor Browser / file revision

 <div style="background: -moz-linear-gradient(black, black 50px, white 50px, white 100px, black 100px, black 150px, white 150px, white 200px);

             background-size: 100px 200px; background-repeat: repeat-x;

             width: 300px; height: 800px;

             margin-bottom: -600px;"></div>

 <!-- making the gradient actually be 300px high isn't reliable since

      the stop positions cannot be exactly represented and rounding errors

      creep in. So just let the gradient be 200px high and pad out to match

      the reference. -->

 <div style="background: black; width: 300px; height: 50px;"></div>

 <div style="background: white; width: 300px; height: 50px;"></div>