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HTML 

              
                <div data-html="[button class='lang' lang='en' data-lang-en='Voir en français']See in english[/button]"></div>
<div class="main" lang="fr">
<div class="intro">
  <h1 data-lang-en="[abbr]HTML[/abbr] semantics">Sémantique <abbr>HTML</abbr></h1>
  <p><em data-lang-en="Get a better understanding of how machines see your code by disabling [abbr]CSS[/abbr]. [button]Disable stylesheets[/button]">On peut simuler la perception de la page par les machines quand <abbr>CSS</abbr> est désactivé. <button>Désactiver le <abbr>CSS</abbr></button></em></p>
</div>
<div class="bloc css">
  <h2 data-lang-en="With a semantic layer">Avec une couche sémantique</h2>
  <div class="content" lang="la">
    <h3>Donec et mollis dolor</h3>
    <p>
      Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor.
    </p>
    <ul>
      <li><a href="#">Nam</a></li>
      <li><a href="#">Tincidunt</li>
      <li><a href="#">Congue</a></li>
    </ul>
    <h3>Donec et mollis dolor</h3>
    <p>
      Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor.
    </p>
    <p>
      Praesent et diam eget libero egestas mattis sit amet vitae augue. Nam tincidunt congue enim, ut porta lorem lacinia consectetur. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus.
    </p>
  </div>
</div><!--
--><div class="bloc css">
  <h2 data-lang-en="Without a semantic layer">Sans couche sémantique</h2>
  <div class="content" lang="la">
    <div class="h3">Donec et mollis dolor</div>
    <div class="p">
      Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor.
    </div>
    <div class="ul">
      <div><a href="#">Nam</a></div>
      <div><a href="#">Tincidunt</a></div>
      <div><a href="#">Congue</a></div>
    </div>
    <div class="h3">Donec et mollis dolor</div>
    <div class="p">
      Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor.
    </div>
    <div class="p">
      Praesent et diam eget libero egestas mattis sit amet vitae augue. Nam tincidunt congue enim, ut porta lorem lacinia consectetur. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus.
    </div>
  </div>
</div>
<div class="outro">
  <p><a href="https://codepen.io/collection/JLacg/" data-lang-en="All other technical demonstrations of front-end concepts">Toutes les autres démonstrations techniques des concepts <i lang="en">front-end</i>.</a></p>
</div>
</div>
!

CSS 

              
                @import "compass/css3";

@import 'compass';

html
{
  background-color: #fdfaf8;
  font-family: "Segoe UI", Candara, "Bitstream Vera Sans", "DejaVu Sans", "Bitstream Vera Sans", "Trebuchet MS", Verdana, "Verdana Ref", sans-serif;
}
body
{
  margin: 1em;
  text-align: center;
}
.bloc
{
  width: 500px;
  border: 1px solid #e7e4e2;
  margin:  1em;
  padding: 2em 2em 1em;
  display: inline-block;
  vertical-align: top;
  text-align: left;
  background-color: white;
  position: relative;
}
h1,
h2
{
  
  margin-top: 0;
}
img
{
  margin: auto;
  display: block;
}
.intro
{
  max-width: 600px;
  margin: auto;
  font-size: 1.5em;
  padding: 4em 0;
  
  em
  {
    font-style: normal;
  }
  button
  {
    display: block;
    margin: 2em auto 0;
    border: 0;
    padding: 1em;
    background-color: #5B537E;
    color: #fff;
    line-height: 1.25;
    font-size: 0.85em;
    transition: background-color 300ms;
    
    &:hover,
    &:focus
    {
      background-color: #706a99;
    }
  }
}
.outro
{
  max-width: 600px;
  margin: auto;
  font-size: 1.5em;
  padding: 2em 0 3em;
  font-weight: bold;
  a
  {
    display: block;
  }
}
a
{
  color: #5B537E;
  transition: color 300ms;
  
  &:hover,
  &:focus,
  &:visited
  {
    color: #706a99;
  }
}
.content
{
  font-family: serif;
  
  a
  {
    color: blue;
  }
}
.css
{
  .content
  {
    font-family: "Segoe UI", Candara, "Bitstream Vera Sans", "DejaVu Sans", "Bitstream Vera Sans", "Trebuchet MS", Verdana, "Verdana Ref", sans-serif;
    
    a
    {
      color: #5B537E;
    }
  }
  
	ul,
  .ul
  {
    @include clearfix;
    padding: 0;
    margin: 0 0 1em;

    & > *
    {
      float: left;
      list-style-type: none;
      margin-right: 2em;
    }
  }
  p,
  .p
  {
    margin: 1em 0;
  }
  h3,
  .h3
  {
    font-size: 1.25em;
    margin: 0.75em 0;
    font-weight: bold;
  } 
}
.lang
{
  position: absolute;
  right:  0;
  top:    0;
  border: 0;
  padding: 0.25em 0.5em;
  background-color: #FFDF7F;
  
  abbr
  {
    border: none;
  }
}
!

JS 

              
                $(function(){
  
  $('.intro').on('click', 'button', function(){

      $('.bloc').toggleClass('css');
    });
  $('[data-html]').each(function(){

    $(this).html($(this).data('html')
                 .replace(/\[/g,'<')
                 .replace(/\]/g,'>')
                 .replace(/'/g,'"'));
  });
  
  var main    = $('.main'),
      strings = $('[data-lang-en]');
  
  var d = new Date();
      d.setTime(d.getTime() + (30*24*60*60*1000));
  var expires = d.toUTCString();
      
	strings.each(function(){

    $(this).data('lang-fr', $(this).html()
                 .replace(/</g, "[")
                 .replace(/>/g, "]")
                 .replace(/"/g, "'"));
  });
  
	$('.lang').on('click', function(){
  	
    if(main.attr('lang') === 'en')
    {
      
      $(this).attr('lang', 'en'); 
      main.attr('lang', 'fr');
      
      document.cookie="demolang=fr; expires="+  expires +"; path=/";
      
      strings.each(function(){
      	$(this).html($(this).data('lang-fr')
                 .replace(/\[/g,'<')
                 .replace(/\]/g,'>')
                 .replace(/'/g,'"'));
      });
    }
    else
    {
      main.attr('lang', 'en');
      $(this).attr('lang', 'fr');
      
      document.cookie="demolang=en; expires="+  expires +"; path=/";
      
      strings.each(function(){
      	$(this).html($(this).data('lang-en')
                 .replace(/\[/g,'<')
                 .replace(/\]/g,'>')
                 .replace(/'/g,'"'));
      });
		}
  });
  
    var cookies = document.cookie.split(';');
  
    for(var i=0; i<cookies.length; i++) {
        var c = cookies[i];
        while (c.charAt(0)==' ') c = c.substring(1);
        if (c.indexOf('demolang=') != -1)
        {
					if(c.substring('demolang='.length, c.length) === 'en')
            {
						$('.lang').trigger('click');
            }
        }
    }
    
});
!
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