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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

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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

The resource you are linking to is using the 'http' protocol, which may not work when the browser is using https.

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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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 

              
                <div class="support-warning">
    This demo requires CSS Grid. The current browser you're using doesn't support it and is using a Flexbox fallback. Find a <a href="https://igalia.github.io/css-grid-layout/enable.html">grid-enabled browser</a>.
</div>

<div class="l-grid l-grid--half-half l-grid--gutter-large l-full-height">
     <div class="l-grid__item l-grid l-grid--gutter-large l-center-center first-panel">
          <div class="content">
          <h2 class="heading">Down the Rabbit Hole</h2>
          <p class="description">Alice was beginning to get very tired of sitting by her sister on the bank, and of having nothing to do: once or twice she had peeped into the book her sister was reading, but it had no pictures or conversations in it, "and what is the use of a book," thought Alice, "without pictures or conversation?" </p>
          </div>
     </div>
     <div class="l-grid__item l-grid l-center-center second-panel">
          <div class="content">
          <h2 class="heading">Advice from a Caterpillar</h2>
          <p class="description">The Caterpillar and Alice looked at each other for some time in silence: at last the Caterpillar took the hookah out of its mouth, and addressed her in a languid, sleepy voice.
“Who are you?” said the Caterpillar.
This was not an encouraging opening for a conversation. Alice replied, rather shyly, “I—I hardly know, Sir, just at present—at least I know who I was when I got up this morning, but I think I must have been changed several times since then.” </p>
          
     </div>
</div>
!

CSS 

              
                * {
     box-sizing: border-box;
}

.support-warning {
     background: #ccb11c;
     color: #000;
     display: block;
     font-family: 'Raleway', sans-serif;
     font-weight: 700;
     opacity: 0.95;
     padding: 3rem;
     position: fixed;
     text-align: center;
     top: 0;
     left: 0;
     width: 100%;
     z-index: 5;
}

.support-warning a {
     color: inherit;
}

body {
   background: #111;
   padding: 1rem; 
}

.l-grid {
     display: flex; 
}

.l-grid--half-half > .l-grid__item {
     flex: 1 1 auto;
}

.l-grid--gutter-large {
     margin-left: -1rem;
}

.l-grid--gutter-large > .l-grid__item {
     margin-left: 1rem;
}


@supports(display: grid) {
     .support-warning {
          display: none;
     }
     
     /* Only the display: grid part needs a feature query */
     .l-grid {
          display: grid;
     } 
     
     /* Reset the margins since we no longer need them */
     .l-grid--gutter-large {
          margin: initial;
     }
     
     .l-grid--gutter-large > .l-grid__item {
          margin: initial;
     }
}

/* Declares two columns 1 fraction each */
.l-grid--half-half {
     grid-template-columns: 1fr 1fr;
}

/* Declares a gutter of 1rem between grid items */
.l-grid--gutter-large {
     grid-gap: 1rem;
}

/* Center the content */
.l-center-center {
     align-items: center;
     justify-content: center;
}

.l-full-height {
     min-height: 100vh;
}

.first-panel {
     background: #4dab6b;
     color: #fff;
}

.second-panel {
     background: #fff;
     color: #111;
}

.content {
     max-width: 300px;
}

.heading {
     font-family: 'Playfair Display', serif;
     font-weight: 700;
     font-size: 2.5rem;
     line-height: 1.2;
     margin-bottom: 1rem;
}

.description {
     font-family: 'Raleway', sans-serif;
     font-weight: 400;
     font-size: 0.9rem;
     line-height: 1.5;
}
!

JS
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999px

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