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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

Add Packages

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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Using packages here is powered by esm.sh, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ESM usage.

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HTML 

              
                <header class="fixed">
  Fixed Header
</header>

<p><a href="#jump">Jump Down</a></p>
<p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Illo atque reiciendis doloribus, consequuntur qui accusamus. Error fugiat sed earum officiis quasi, minus blanditiis aliquid illum quibusdam dolorum omnis incidunt deserunt.</p>
<p>Provident molestias est amet praesentium sunt esse quisquam, accusamus nulla maxime repellendus unde et nisi similique quam debitis laboriosam quidem illo iusto optio officiis a dolor! Quo eligendi sint quam!</p>
<p>Earum veritatis porro nesciunt maxime molestiae, accusamus doloremque quisquam deserunt obcaecati assumenda voluptates, et aliquid quasi laborum officiis deleniti aut eveniet similique, consectetur nulla sequi voluptas. Sapiente maiores velit ea?</p>
<p>Sed, possimus. Iure quos odio unde dignissimos, amet illum impedit molestiae non doloribus recusandae dolores facilis magni aspernatur vel excepturi, dicta vitae voluptas, quas assumenda commodi! At tenetur commodi eos!</p>
<p>Veniam maxime aliquid harum! Ad quo debitis vel nesciunt nihil adipisci voluptatem totam laboriosam, culpa reprehenderit iure ut id amet ullam quasi quaerat veniam cumque iste necessitatibus repellendus vitae maiores?</p>
<p>Accusantium sit laudantium ea dolore sed recusandae dolor ad magni numquam repellat consectetur maxime quo doloribus odit fuga, laborum distinctio, enim tempora obcaecati. Architecto voluptatibus optio quisquam fugit tempora accusantium!</p>
<p>Commodi, excepturi aliquam error vitae qui, corrupti ad quod eligendi, sapiente alias provident aliquid pariatur quaerat voluptates ex. Veritatis impedit quam vero nemo reiciendis voluptates repellat tempora, doloribus porro ea.</p>
<p>Iusto deleniti, explicabo, blanditiis ipsam fugiat quidem similique natus nostrum neque hic quaerat quo, quibusdam sapiente eveniet rem possimus consequatur ut reprehenderit dignissimos porro! Placeat dolor quod sequi quam dignissimos?</p>
<p>Sequi omnis dolores, numquam voluptate atque ratione nulla, doloremque ipsa commodi laborum ut in vero praesentium voluptatem corrupti iure, corporis quis explicabo sit? Aliquid eos eum unde repellat, quas architecto.</p>
<p>Iste magnam adipisci nam maxime, sit suscipit temporibus aperiam, possimus recusandae quibusdam voluptate? Numquam ad sunt nam illum cumque ea provident nemo, velit exercitationem perferendis, architecto totam ipsam ex eum!</p>
<p>Necessitatibus, ratione adipisci. Sapiente cumque molestias id. Nihil, beatae velit impedit officia placeat corrupti inventore facere doloribus suscipit autem est repellendus nam nemo, iste, nisi vel nobis eos ratione? Placeat.</p>
<h3 id="jump">Header</h3>
<p>Nam aut iure eaque, eligendi itaque necessitatibus quasi reiciendis similique deleniti ipsum vel. Exercitationem, nisi, saepe consectetur recusandae impedit corporis consequuntur obcaecati fuga, deleniti ipsa repudiandae beatae dolor cum aut?</p>
<p>Recusandae, tempora? Aspernatur voluptatibus repellat, atque vero in numquam beatae et amet nesciunt, ipsa ea nulla quidem molestiae magnam porro nihil at eaque dicta consequuntur dolore minus a est aperiam.</p>
<p>Esse, commodi, est nam molestias impedit natus praesentium voluptate dignissimos iste aliquam distinctio culpa sint cupiditate eaque adipisci similique officia ipsa? Quo minus voluptatem quas praesentium exercitationem, nobis soluta error?</p>
<p>Accusantium, repudiandae saepe. Inventore dolore fugiat quibusdam maxime autem, officia voluptatibus soluta eaque. Ipsam, omnis molestiae iusto fuga illum similique tempora maiores voluptates voluptatem laborum, itaque debitis velit adipisci eveniet!</p>
<p>Sed dolores ad necessitatibus possimus eius saepe mollitia. Quam, commodi corrupti eius rerum fugiat ab aperiam consequatur voluptatum veniam assumenda ea eos. Ipsum, cumque! Delectus rem accusantium voluptate odit non.</p>
<p>Dicta odit deleniti sequi fuga voluptate animi reprehenderit sunt quod veritatis tenetur alias quibusdam ipsam commodi error quas, adipisci eveniet dolores distinctio beatae nulla eum iste dignissimos. Illum, enim fugiat?</p>
<p>Deleniti similique iure eius officiis atque, delectus dolorum quis ullam veniam magnam at quae ea rerum officia, ipsum quos quasi laborum sapiente ipsa unde. Minima asperiores earum ipsa excepturi in.</p>
<p>Voluptatibus pariatur officia veritatis aperiam sapiente sint libero consequatur animi iusto vitae voluptates laudantium sit, fugiat minus cum ratione a! Consequuntur quasi vitae ex ratione sapiente qui nostrum voluptatem unde?</p>
<p>Ipsum modi est culpa, in quo inventore. Praesentium, doloremque doloribus! Numquam atque, voluptatum iusto commodi assumenda modi sequi ea consequuntur vel, earum tenetur rem, deserunt sit quia fugit magnam porro!</p>
!

CSS 

              
                header.fixed {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  padding: 30px;
  background: orange;
  text-align: center;
}

html {
  --top-spacing: 100px;
  scroll-padding-top: var(--top-spacing);
}

body {
  margin: var(--top-spacing) auto;
  
  max-width: 400px;
  padding: 0 20px;
  font: 18px/1.4 system-ui;
}
!

JS
!
999px

Console