gistfile1.txt

<div class="l-container">

  <div class="l-8">

    <ul class="o-list">
      <li class="o-list__item">Tekst</li>
    </ul>
    
  </div>
  
  <div class="l-4">
    
    <ul class="o-list">
      <li class="o-list__item">Tekst</li>
    </ul>
    
  </div>
  
</div>



CSS:
.l-container {
  has a clearfix of course
}

.l-4 {
  float: left;
  width: 33%;
}

.l-8 {
  float: left;
  width: 66%;
}

.o-list:container(width >= 600px) {
  color: red;
}