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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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Adding Classes

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. So you don't have access to higher-up elements like the <html> tag. If you want to add classes there that can affect the whole document, this is the place to do it.

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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Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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HTML 

              
                <div class="container">
  <div class="header col-md-12">
    <h1 class="text-primary">Isaac Newton</h1>
  </div>

  <div class="row">
    <div class="sidebar col-md-2">
      <ul>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
      </ul>
    </div>

    <div class="main col-md-8">
        <img src="https://r.hswstatic.com/w_907/gif/missedinhistory-98-2015-11-isaac-newton-post-600x350.jpg" alt="Isaac Newton passes white light through a prism to create a spectral rainbow." />
        <p class="caption">Sir Isaac Newton (25 December 1642 – 20 March 1726) was an English natural philosopher who is widely recognised as one of the most influential scientists of all time and a key figure in the scientific revolution.</p>

      <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut sed sem convallis, elementum nisl at, imperdiet sapien. Aliquam arcu elit, consequat in risus a, maximus facilisis arcu. Etiam feugiat tortor vitae pretium porttitor. Maecenas laoreet ligula luctus nibh luctus, finibus mattis est tempor. Cras ornare, ipsum non dictum vulputate, enim nulla ultricies magna, id condimentum nibh justo at lectus. In quis nisi ac mi aliquet convallis. Vivamus efficitur, velit at faucibus tristique, eros tellus convallis justo, at pretium nisi purus id augue. Ut vulputate sem eget scelerisque ornare. Interdum et malesuada fames ac ante ipsum primis in faucibus. Donec et consequat sapien. Morbi eget nulla ultricies, sodales mi vel, sollicitudin ligula. Donec pharetra purus lorem, in ornare leo imperdiet vel. Nulla sodales laoreet lectus id efficitur. Sed non quam aliquet mauris fringilla maximus.</p>

<p>Sed bibendum sodales placerat. Integer et lorem nec dui posuere convallis quis id ante. Duis fermentum odio in ex pharetra efficitur. Duis hendrerit ut quam vel volutpat. Sed dui orci, mattis lacinia pellentesque eu, viverra a lacus. Cras faucibus, sapien vitae vulputate rhoncus, dui velit hendrerit sem, nec luctus sem nibh ut quam. Proin molestie, nisl ut placerat auctor, nisi augue ultricies nisi, quis convallis purus ex quis sapien. Cras ac sagittis dui, in tempor dolor. Aliquam lobortis mi sed est rhoncus tempus. Aenean mollis vulputate lacinia. Curabitur nec luctus mi. Aliquam vitae feugiat ligula. Pellentesque id imperdiet turpis, nec vehicula tellus. Morbi sodales elementum commodo. Morbi bibendum lorem sed convallis congue. Phasellus at dolor quis metus feugiat fringilla.</p>

<p>Maecenas faucibus pretium metus, et sollicitudin felis volutpat in. Donec ultrices dictum orci ut consectetur. Maecenas pretium dolor enim, et egestas tortor ultrices vitae. Aliquam sit amet aliquet neque. Sed sed maximus felis. Sed et dolor vitae leo feugiat efficitur. Morbi id urna nec ante sollicitudin feugiat non non massa. Donec non elit pellentesque, dapibus quam vitae, iaculis sapien. Donec pellentesque arcu et mattis vulputate. Donec pulvinar hendrerit leo sit amet malesuada. Donec lectus sapien, sollicitudin in ornare in, pulvinar nec velit. Morbi consectetur accumsan lorem, id mollis metus sagittis at. In faucibus ac nibh quis condimentum. Mauris tortor lorem, vulputate ut vestibulum et, fermentum sed turpis.</p>

<p>Morbi tincidunt arcu turpis. Duis ut iaculis nisl, vehicula consectetur tellus. Vestibulum blandit massa ut magna vehicula egestas. Nam arcu ligula, commodo fermentum odio a, fermentum hendrerit risus. Curabitur enim risus, tempor sed sem eu, sollicitudin scelerisque mi. Donec elementum aliquam ex, a lacinia lectus pharetra ut. Donec vitae ante ut turpis dictum dignissim. Donec ut turpis consectetur, feugiat orci quis, sodales velit.</p>

Nam pretium ullamcorper lorem. Aenean scelerisque nulla sit amet condimentum pharetra. Sed consequat pretium sem, a fringilla quam mollis quis. Nullam scelerisque vel massa eget pretium. Donec consequat ex sit amet pellentesque varius. In justo ligula, tincidunt eget cursus porttitor, interdum vitae justo. Sed nec nisl placerat, blandit nunc sit amet, porta mauris.</p>
    </div>
    <div class="sidebar col-md-2">
     <ul>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
        <li><a href="#">Links</a></li>
      </ul>
    </div>
  </div>
</div>
!

CSS 

              
                body {
  background-color: #a3d5d3;
}
h1 {text-align: center;}

img {
  margin: auto;
  width: 100%;
}
.caption {
  text-align: justify;
  border: 2px solid blue;
  background-color: white;
}

div {  
  border: 2px solid blue;}

.sidebar {text-align: center;
  border: 2px solid blue;}
!

JS 

              
                document.getElementsByTagName("h1")[0].style.fontSize = "80px";

$("img").addClass("img-responsive");
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999px

Console