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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>

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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

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JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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HTML 

              
                <nav class="nav-collapse" role="navigation">
    <ul class="tabs primary-nav">
        <li class="tabs__item">
            <a href="#" class="tabs__link">Home</a>
        </li>
        <li class="tabs__item">
            <a href="#" class="tabs__link">Talks</a>
        </li>
        <li class="tabs__item">
            <a href="#" class="tabs__link">Schedule</a>
        </li>
        <li class="tabs__item">
            <a href="#" class="tabs__link">Location</a>
        </li>
        <li class="tabs__item">
            <a href="#" class="tabs__link">Contact</a>
        </li>
    </ul>
</nav>
!

CSS 

              
                @import url(https://fonts.googleapis.com/css?family=Share:400,700&subset=latin,latin-ext);

* {
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  padding: 0;
  margin: 0;
}

html {
    font: 0.75em/1.5 sans-serif;
    background: #000;
    margin-top: 50px;
}

/**
 * Tabs object.
 *
 * 1. Tables (kinda) for layout!
 * 2. This is the magic bit; make all children occupy equal width.
 * 3. Required to make the tabs fill their container.
 * 4. Make each tab pack up horizontally.
 * 5. Ensure the hit area covers the whole tab.
 */
.tabs {
    margin:  0;
    padding: 0;
    list-style: none;
    display: table; /* [1] */
    table-layout: fixed; /* [2] */
    width: 100%; /* [3] */
}

    .tabs__item {
        width: 100%;
        float: left;
    }

    @media screen and (min-width: 40em) {
        .tabs__item {
          display: table-cell; /* [4] */
          float: none;
          width: auto;
        }
    }

        .tabs__link {
            display: block; /* [5] */
        }


/**
 * Primary nav. Extends `.tabs`.
 *
 * 1. Stop tabs’ corners leaking out beyond our 4px round.
 */
.primary-nav {
    text-align: center;
    border-radius: 0;
    overflow: hidden; /* [1] */
}

        .primary-nav a {
            padding: .75em 1em;
            color: white;
            background: rgba(255, 255, 255, 0.1);
            color: #fff;
            text-decoration: none;
            border-right: 1px solid #000;
            font-family: Share, Helvetica, Arial, sans-serif;
            font-weight: 400;
            font-size: 1.75em;
        }

        .primary-nav a:hover {
            color: black;
            background: #f8d800;
        }

/* Responsive-nav.js */

.js .nav-collapse {
  clip: rect(0 0 0 0);
  max-height: 0;
  position: absolute;
  display: block;
  overflow: hidden;
  zoom: 1;
}

.nav-collapse.opened {
  max-height: 9999px;
}

.disable-pointer-events {
  pointer-events: none !important;
}

.nav-toggle {
  -webkit-tap-highlight-color: rgba(0,0,0,0);
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  -o-user-select: none;
  user-select: none;
}

@media screen and (min-width: 40em) {
  .js .nav-collapse {
    position: relative;
  }
  .js .nav-collapse.closed {
    max-height: none;
  }
  .nav-toggle {
    display: none;
  }
}

.nav-collapse {
  list-style: none;
  width: 100%;
  float: left;
}

.fixed {
  position: fixed;
  width: 100%;
  top: 0;
  left: 0;
}

.nav-toggle {
  position: fixed;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
  text-decoration: none;
  text-indent: -999px;
  position: relative;
  overflow: hidden;
  width: 70px;
  height: 55px;
  float: right;
}

.nav-toggle:before {
  color: #f8d800; /* Edit this to change the icon color */
  font-family: "responsivenav", sans-serif;
  font-style: normal;
  font-weight: normal;
  font-variant: normal;
  font-size: 28px;
  text-transform: none;
  position: absolute;
  content: "≡";
  text-indent: 0;
  text-align: center;
  line-height: 55px;
  speak: none;
  width: 100%;
  top: 0;
  left: 0;
}

.nav-toggle.active::before {
  font-size: 24px;
  content:"x";
}
!

JS 

              
                var navigation = responsiveNav(".nav-collapse", {
  animate: true,                    // Boolean: Use CSS3 transitions, true or false
  transition: 284,                  // Integer: Speed of the transition, in milliseconds
  label: "Menu",                    // String: Label for the navigation toggle
  insert: "before",                  // String: Insert the toggle before or after the navigation
  customToggle: "",                 // Selector: Specify the ID of a custom toggle
  closeOnNavClick: false,           // Boolean: Close the navigation when one of the links are clicked
  openPos: "relative",              // String: Position of the opened nav, relative or static
  navClass: "nav-collapse",         // String: Default CSS class. If changed, you need to edit the CSS too!
  navActiveClass: "js-nav-active",  // String: Class that is added to <html> element when nav is active
  jsClass: "js",                    // String: 'JS enabled' class which is added to <html> element
  init: function(){},               // Function: Init callback
  open: function(){},               // Function: Open callback
  close: function(){}               // Function: Close callback
});
!
999px

Console