<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <link rel="stylesheet" href="style.css">
  <title>BOX!!</title>

</head>
<body>
  <div>box </div>
</body>
</html>
div{
  width: 100%;
  height: 30px;
  background-color: skyblue;
}

External CSS

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External JavaScript

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