JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
<div class="fixed-top">
    <div class="middle">aaaaaaaaaaaaaaa</div>
</div>
<!-- Button trigger modal -->
<button type="button" class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">
  Launch demo modal
</button>

<p>
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quasi accusantium sunt beatae id obcaecati suscipit debitis fugiat dolor laudantium voluptatem similique molestias fuga consequatur. Dolorum modi amet veritatis distinctio eius.
  </p>
          <p>
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quasi accusantium sunt beatae id obcaecati suscipit debitis fugiat dolor laudantium voluptatem similique molestias fuga consequatur. Dolorum modi amet veritatis distinctio eius.
  </p>
          <p>
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quasi accusantium sunt beatae id obcaecati suscipit debitis fugiat dolor laudantium voluptatem similique molestias fuga consequatur. Dolorum modi amet veritatis distinctio eius.
  </p>
          <p>
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quasi accusantium sunt beatae id obcaecati suscipit debitis fugiat dolor laudantium voluptatem similique molestias fuga consequatur. Dolorum modi amet veritatis distinctio eius.
  </p>
          <p>
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quasi accusantium sunt beatae id obcaecati suscipit debitis fugiat dolor laudantium voluptatem similique molestias fuga consequatur. Dolorum modi amet veritatis distinctio eius.
  </p>
          <p>
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quasi accusantium sunt beatae id obcaecati suscipit debitis fugiat dolor laudantium voluptatem similique molestias fuga consequatur. Dolorum modi amet veritatis distinctio eius.
  </p>
         ...

CSS

.btn {
    margin-top: 50px;
}

.fixed-top {
    top: 0;
    left: 0;
    right: 0;
    height: 50px;
    background: red;
}
.middle {
    max-width: 480px;
    margin: 0px auto !important;
}