Try it Yourself: CSS Height / Width

CSS Height / Width

<!DOCTYPE html>
<html>
<head>
<style>
.banner {
  width: 100%;
  height: 240px;
}

.thumbnail {
  width: 150px;
  height: 150px;
}
</style>
</head>
<body>

<div class="banner">Banner</div>
<div class="thumbnail">Thumb</div>

</body>
</html>

<!DOCTYPE html>
<html>
<head>
<style>
.banner {
  width: 100%;
  height: 240px;
}

.thumbnail {
  width: 150px;
  height: 150px;
}
</style>
</head>
<body>

<div class="banner">Banner</div>
<div class="thumbnail">Thumb</div>

</body>
</html>