Редактор кода W3Schools - Tryit

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
* {
  box-sizing: border-box;
}

.header {
  border: 1px solid red;
  padding: 15px;
}

.row::after {
  content: "";
  clear: both;
  display: table;
}

[class*="col-"] {
  float: left;
  padding: 15px;
  border: 1px solid red;
}

.col-1 {width: 8.33%;}
.col-2 {width: 16.66%;}
.col-3 {width: 25%;}
.col-4 {width: 33.33%;}
.col-5 {width: 41.66%;}
.col-6 {width: 50%;}
.col-7 {width: 58.33%;}
.col-8 {width: 66.66%;}
.col-9 {width: 75%;}
.col-10 {width: 83.33%;}
.col-11 {width: 91.66%;}
.col-12 {width: 100%;}
</style>
</head>
<body>

<div class="header">
  <h1>Chania</h1>
</div>

<div class="col-3">
  <ul>
    <li>The Flight</li>
    <li>The City</li>
    <li>The Island</li>
    <li>The Food</li>
  </ul>
</div>

<div class="col-9">
  <h1>The City</h1>
  <p>Chania is the capital of the Chania region on the island of Crete. The city can be divided in two parts, the old town and the modern city.</p>
  <p>Измените размер окна браузера, чтобы увидеть, как контент реагирует на изменение размера.</p>
</div>

</div>

</body>
</html>

​x
 
<!DOCTYPE html><html><head><meta name="viewport" content="width=device-width, initial-scale=1.0"><style>* {  box-sizing: border-box;}​.header {  border: 1px solid red;  padding: 15px;}​.row::after {  content: "";  clear: both;  display: table;}​[class*="col-"] {  float: left;  padding: 15px;  border: 1px solid red;}​.col-1 {width: 8.33%;}.col-2 {width: 16.66%;}.col-3 {width: 25%;}.col-4 {width: 33.33%;}.col-5 {width: 41.66%;}.col-6 {width: 50%;}.col-7 {width: 58.33%;}.col-8 {width: 66.66%;}.col-9 {width: 75%;}.col-10 {width: 83.33%;}.col-11 {width: 91.66%;}.col-12 {width: 100%;}</style></head><body>​<div class="header">  <h1>Chania</h1></div>​<div class="row">​<div class="col-3">  <ul>    <li>The Flight</li>    <li>The City</li>    <li>The Island</li>    <li>The Food</li>  </ul></div>​<div class="col-9">  <h1>The City</h1>  <p>Chania is the capital of the Chania region on the island of Crete. The city can be divided in two parts, the old town and the modern city.</p>  <p>Измените размер окна браузера, чтобы увидеть, как контент реагирует на изменение размера.</p></div>​</div>​</body></html>                