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HTML

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About the <head>

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CSS

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CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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HTML 

              
                <div class="header">
  <h1>H1 Main Header</h1>
</div>

<div class="content">
  <h2>H2 Section heading</h2>
  
  <p>
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
  </p>
  
  <h3>H3 Subheading</h3>
  
  <p>
  Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage, and going through the cites of the word in classical literature, discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.
  </p>
</div>

<div class="sidebar">
  <h2>H2 Side menu</h2>
  <ul>
    <li><a href="#">Sidebar link</a></li>
    <li><a href="#">Sidebar link</a></li>
    <li><a href="#">Sidebar link</a></li>
    <li><a href="#">Sidebar link</a></li>
    <li><a href="#">Sidebar link</a></li>
  </ul>
</div>

<footer class="footer">
  <p>Demo by Adrian Sandu. <a href="http://www.sitepoint.com/understanding-and-using-rem-units-in-css" target="_blank">See article</a>.</p>
</footer>
!

CSS 

              
                /* Document level adjustments */
html {
  font-size: 17px;
  font-family: Arial, sans-serif;
}
body {
  padding: 0 1rem;
}
h1 {
  margin-top: 0;
}
@media (max-width: 900px) {
  html { font-size: 15px; }
}
@media (max-width: 400px) {
  html { font-size: 13px; }
}

/* Modules will scale with document */
.header {
  font-size: 1.5rem;
}
.footer {
  font-size: 0.75rem;
}
.sidebar {
  font-size: 0.85rem;
}

/* Type will scale with modules */
h1 {
  font-size: 3em;
}
h2 {
  font-size: 2.5em;
}
h3 {
  font-size: 2em;
}

/* layout */

.content {
  float: left;
  width: 70%;
}

.sidebar {
  float: right;
  width: 25%;
}

.footer {
  clear: both;
  padding-top: 2em;
  border-top: solid 1px #ccc;
}
@media (max-width: 900px) {
  .content { width: 60%; }
  .sidebar { width: 40%; }
}
@media (max-width: 400px) {
  .content, .sidebar { float: none; width: auto; }
}
!

JS
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