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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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About the <head>

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. If you need things in the <head> of the document, put that code here.

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Insecure Resource

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CSS

About CSS Preprocessors

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

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

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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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Packages

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HTML 

              
                <header role="banner">
  <h1>Site Title</h1>
  <nav role="navigation" class="navbar">
    <a href="#">Link</a>
    <a href="#">Link</a>
    <a href="#">Link</a>
    <a href="#">Link</a>
  </nav>
</header>

<!--
content by [Batman Ipsum](http://idsgn.dropmark.com/107/1460961)
-->

<main role="main">
  <h1>Page Title</h1>
  <P>I thought this might be a good opportunity for... improving the foundations.</p>
  <p>You are in hell, little man. And I am the devil.</p>
  <p>Now, our operation is small but there is a lot of potential for aggressive expansion. So which of you fine gentlemen would like to join our team? Oh. There's only one spot open right now, so we're gonna have... tryouts.</p>
</main>

<aside role="complementary">
  <h2>Sidebar</h2>
  <p>Yes. The fire rises.</p>
  <p>You must become more than just a man in the mind of you opponent.</p>
  <p>You want order in Gotham. Batman must take off his mask and turn himself in. Oh, and every day he doesn't, people will die. Starting tonight. I'm a man of my word.<P>
</aside>
    
<footer role="contentinfo">
  <small>I am the League of Shadows.</small>
</footer>
!

CSS 

              
                html { box-sizing: border-box; }
*, *:before, *:after { box-sizing: inherit; }

header, main, aside, footer {
  padding: 1rem;
}

header[role="banner"] {
  text-align: center;
}

.navbar a {
  display: inline-block;
  color: inherit;
  text-decoration: none;
  width: 7em;
  border-right: 1px solid red;
}

.navbar a:last-of-type {
  border-right: none;
}

/* 
  demonstration:
  display: table makes responsiveness easy!
*/
@media (min-width: 40em) {

  main, aside {
    display: table-cell;
  }

  main {
    width: 70%;
  }

}
!

JS
!
999px

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