Untitled

<!DOCTYPE html>
<html>

  <head>
    <link data-require="bootstrap@*" data-semver="3.3.2" rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css" />
    <script data-require="bootstrap@*" data-semver="3.3.2" src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
    <script data-require="jquery@2.1.3" data-semver="2.1.3" src="http://code.jquery.com/jquery-2.1.3.min.js"></script>
    <link rel="stylesheet" href="style.css" />
    <script src="script.js"></script>
  </head>

  <body class="row">
    <div class="col-sm-4 btn-danger">One third across on medium screens but 100% on smaller screens.</div>
    <div class="col-sm-4 btn-info">One third across on medium screens but 100% on smaller screens.</div>
    <div class="col-sm-4 btn-warning">One third across on medium screens but 100% on smaller screens.</div>
  </body>
</html>

// Code goes here

/* Styles go here */