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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.

!
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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HTML 

              
                <html>
  <body>
    <div id="announcement"><div class="container">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Curabitur posuere nisl in nunc euismod, sit amet porttitor ex accumsan. Quisque nec magna nisi. Integer porta odio quis felis mattis, vitae bibendum lorem maximus. Fusce luctus neque orci, ut pellentesque velit auctor eu. Proin iaculis nunc sed fringilla semper. Vestibulum ipsum lacus, placerat vitae lorem non, condimentum sagittis nibh. Mauris sagittis vulputate mi. Vestibulum ante ipsum primis </div></div>
    <div id="header"><div class="container">
      This is fixed and needs to stick when it reaches the top.
    </div></div>
    <div id="main"><div class="container">
      <p>Aut commodo massa diam quis elit. Vestibulum euismod vitae justo nec tempus. Duis venenatis venenatis arcu, sit amet varius libero. Nullam porta arcu at massa iaculis, at feugiat erat blandit. Vestibulum in tincidunt justo. Vivamus eget mollis arcu, ac aliquet ipsum.</p>

<p>Pellentesque diam metus, pretium nec odio vel, fermentum feugiat lectus. Aenean lacus est, dignissim ut accumsan faucibus, vehicula vel diam. Donec arcu justo, sodales nec nibh in, lobortis sollicitudin neque. Vivamus suscipit velit pulvinar sem imperdiet, vitae porttitor diam euismod. Ut mauris est, consequat at feugiat vel, mattis nec quam. Ut dictum erat vitae ullamcorper fringilla. Cras et lorem at dui pulvinar condimentum vel id justo. Duis sagittis quam nec erat euismod, tempus elementum dui mollis. Morbi eu nisl ultricies, imperdiet tellus sodales, lacinia quam.</p>

<p>Pellentesque diam metus, pretium nec odio vel, fermentum feugiat lectus. Aenean lacus est, dignissim ut accumsan faucibus, vehicula vel diam. Donec arcu justo, sodales nec nibh in, lobortis sollicitudin neque. Vivamus suscipit velit pulvinar sem imperdiet, vitae porttitor diam euismod. Ut mauris est, consequat at feugiat vel, mattis nec quam. Ut dictum erat vitae ullamcorper fringilla. Cras et lorem at dui pulvinar condimentum vel id justo. Duis sagittis quam nec erat euismod, tempus elementum dui mollis. Morbi eu nisl ultricies, imperdiet tellus sodales, lacinia quam.</p>

<p>Pellentesque diam metus, pretium nec odio vel, fermentum feugiat lectus. Aenean lacus est, dignissim ut accumsan faucibus, vehicula vel diam. Donec arcu justo, sodales nec nibh in, lobortis sollicitudin neque. Vivamus suscipit velit pulvinar sem imperdiet, vitae porttitor diam euismod. Ut mauris est, consequat at feugiat vel, mattis nec quam. Ut dictum erat vitae ullamcorper fringilla. Cras et lorem at dui pulvinar condimentum vel id justo. Duis sagittis quam nec erat euismod, tempus elementum dui mollis. Morbi eu nisl ultricies, imperdiet tellus sodales, lacinia quam.</p>

<p>Pellentesque diam metus, pretium nec odio vel, fermentum feugiat lectus. Aenean lacus est, dignissim ut accumsan faucibus, vehicula vel diam. Donec arcu justo, sodales nec nibh in, lobortis sollicitudin neque. Vivamus suscipit velit pulvinar sem imperdiet, vitae porttitor diam euismod. Ut mauris est, consequat at feugiat vel, mattis nec quam. Ut dictum erat vitae ullamcorper fringilla. Cras et lorem at dui pulvinar condimentum vel id justo. Duis sagittis quam nec erat euismod, tempus elementum dui mollis. Morbi eu nisl ultricies, imperdiet tellus sodales, lacinia quam.</p>

<p>Pellentesque diam metus, pretium nec odio vel, fermentum feugiat lectus. Aenean lacus est, dignissim ut accumsan faucibus, vehicula vel diam. Donec arcu justo, sodales nec nibh in, lobortis sollicitudin neque. Vivamus suscipit velit pulvinar sem imperdiet, vitae porttitor diam euismod. Ut mauris est, consequat at feugiat vel, mattis nec quam. Ut dictum erat vitae ullamcorper fringilla. Cras et lorem at dui pulvinar condimentum vel id justo. Duis sagittis quam nec erat euismod, tempus elementum dui mollis. Morbi eu nisl ultricies, imperdiet tellus sodales, lacinia quam.</p>

<p>Pellentesque diam metus, pretium nec odio vel, fermentum feugiat lectus. Aenean lacus est, dignissim ut accumsan faucibus, vehicula vel diam. Donec arcu justo, sodales nec nibh in, lobortis sollicitudin neque. Vivamus suscipit velit pulvinar sem imperdiet, vitae porttitor diam euismod. Ut mauris est, consequat at feugiat vel, mattis nec quam. Ut dictum erat vitae ullamcorper fringilla. Cras et lorem at dui pulvinar condimentum vel id justo. Duis sagittis quam nec erat euismod, tempus elementum dui mollis. Morbi eu nisl ultricies, imperdiet tellus sodales, lacinia quam.</p>

<p>Sed tempor, eros ut gravida ultricies, eros ex scelerisque arcu, in sodales ex ex eu diam. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Curabitur lorem lectus, tincidunt lacinia felis quis, pulvinar sodales eros. Praesent diam nulla, commodo at semper at, lacinia quis velit. Quisque consequat tortor vel scelerisque viverra. Morbi vel finibus nisl. Aliquam eget dui non ligula pharetra sagittis. Curabitur vel porttitor ipsum. Cras imperdiet egestas posuere. Integer urna lacus, tristique a rutrum sed, malesuada in purus. Suspendisse potenti. In ullamcorper nisi mi.</p>
    </div></div>
  </body>
</html>
!

CSS 

              
                body {
  font-family: Arial;
  padding: 0;
  margin: 0;
}
#announcement {
  background: #ff0000;
  color: navy;
  padding: 20px 0px;
}
#header {
  background-color: black;
  color: white;
  line-height: 58px;
  width: 100%;
  position: fixed;
  height: 58px;
}
#main {
  padding: 20px 0px;
  margin-top: 58px; /* Header Height */
}
.container {
  max-width: 700px;
  margin: 0px auto;
}
!

JS 

              
                var requestId = null;

window.addEventListener("resize", function() {
  if (!requestId) {
    requestId = requestAnimationFrame(resize);
  }
});

function resize() {
  // this is just needed for codepen because you can resize viewport to zero and it would throw off calculations
  if (window.innerWidth < 10) {
    requestId = null;
    return;
  }   
  
  // Drag header up with announcement
  var announcement = document.getElementById('announcement');
  gsap.fromTo('#header', { top: () => announcement.offsetHeight }, {
      top: 0,
      ease: 'none',
      scrollTrigger: {
        trigger: '#announcement',  
        start: 'top top',
        end: 'bottom top',
        scrub: true,
        invalidateOnRefresh: true
      }
    });

  requestId = null;
}

 window.addEventListener('DOMContentLoaded', (event) => {
   resize();
 });
!
999px

Console