Try it Yourself: RWD Media Queries

RWD Media Queries

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
.sidebar {
  width: 25%;
  float: left;
}

@media (max-width: 768px) {
  .sidebar {
    width: 100%;
    float: none;
  }
}
</style>
</head>
<body>

</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
.sidebar {
  width: 25%;
  float: left;
}

@media (max-width: 768px) {
  .sidebar {
    width: 100%;
    float: none;
  }
}
</style>
</head>
<body>

</body>
</html>