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CSS

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HTML 

              
                <div id="wrap">
  <header role="banner">
    <h1>Hide the sidebar!</h1>
    <a
      href="http://twitter.com/genelocklin"
      title="follow me for more awesome shit"
      >by @genelocklin</a
    >
  </header>

  <nav role="navigation"></nav>

  <input type="checkbox" id="width_sidebar" role="button" />
  <label for="width_sidebar" onclick=""
    ><span>hide the sidebar</span><span>&raquo;</span
    ><span>&laquo;</span></label
  >

  <div role="main">
    <article class="post">
      <h1 itemprop="headline">Hide the Sidebar!</h1>
      <p>Toggle the button to the right, to hide the sidebar.</p>
      <h2>The Pandorica Opens</h2>
      <p>
        Father Christmas. Santa Claus. Or as I've always known him: Jeff. I'm
        the Doctor. Well, they call me the Doctor. I don't know why. I call me
        the Doctor too. I still don't know why. I hate yogurt. It's just stuff
        with bits in. It's art! A statement on modern society, 'Oh Ain't Modern
        Society Awful?'! I am the Doctor, and you are the Daleks!
      </p>
      <h3>Planet of the Dead</h3>
      <p>
        Aw, you're all Mr. Grumpy Face today. You've swallowed a planet! The way
        I see it, every life is a pile of good things and bad
        things.&hellip;hey.&hellip;the good things don't always soften the bad
        things; but vice-versa the bad things don't necessarily spoil the good
        things and make them unimportant. You hate me; you want to kill me!
        Well, go on! Kill me! KILL ME! Annihilate? No. No violence. I won't
        stand for it. Not now, not ever, do you understand me?! I'm the Doctor,
        the Oncoming Storm - and you basically meant beat them in a football
        match, didn't you? It's art! A statement on modern society, 'Oh Ain't
        Modern Society Awful?'!
      </p>
      <h4>The Waters of Mars</h4>
      <p>
        The way I see it, every life is a pile of good things and bad
        things.&hellip;hey.&hellip;the good things don't always soften the bad
        things; but vice-versa the bad things don't necessarily spoil the good
        things and make them unimportant. You hit me with a cricket bat.
        Heh-haa! Super squeaky bum time! Stop talking, brain thinking. Hush. I'm
        the Doctor, I'm worse than everyone's aunt. *catches himself* And that
        is not how I'm introducing myself.
      </p>
      <h5>The Stolen Earth</h5>
      <p>
        Heh-haa! Super squeaky bum time! You hate me; you want to kill me! Well,
        go on! Kill me! KILL ME! You hate me; you want to kill me! Well, go on!
        Kill me! KILL ME! It's a fez. I wear a fez now. Fezes are cool.
      </p>
      <h6>Amy's Choice</h6>
      <p>
        I'm the Doctor. Well, they call me the Doctor. I don't know why. I call
        me the Doctor too. I still don't know why. Heh-haa! Super squeaky bum
        time! Did I mention we have comfy chairs? I'm the Doctor, I'm worse than
        everyone's aunt. *catches himself* And that is not how I'm introducing
        myself.
      </p>
    </article>
    <!-- /post -->
  </div>
  <!-- /main -->

  <aside role="complimentary">
    <h2>
      <a href="http://twitter.com/genelocklin" title="follow gene locklin"
        >Follow me on Twitter</a
      >
    </h2>
    <p>
      <a
        href="https://twitter.com/share"
        class="twitter-share-button"
        data-size="large"
        data-via="genelocklin"
        data-count="none"
        >Tweet</a
      >
      <a
        href="https://twitter.com/genelocklin"
        class="twitter-follow-button"
        data-show-count="false"
        data-size="large"
        >Follow @genelocklin</a
      >
    </p>
    <p>
      Father Christmas. Santa Claus. Or as I've always known him: Jeff. I'm the
      Doctor. Well, they call me the Doctor. I don't know why. I call me the
      Doctor too. I still don't know why. I hate yogurt. It's just stuff with
      bits in. It's art! A statement on modern society, 'Oh Ain't Modern Society
      Awful?'! I am the Doctor, and you are the Daleks!
    </p>
    <p>
      Aw, you're all Mr. Grumpy Face today. You've swallowed a planet! The way I
      see it, every life is a pile of good things and bad
      things.&hellip;hey.&hellip;the good things don't always soften the bad
      things; but vice-versa the bad things don't necessarily spoil the good
      things and make them unimportant. You hate me; you want to kill me! Well,
      go on! Kill me! KILL ME! Annihilate? No. No violence. I won't stand for
      it. Not now, not ever, do you understand me?! I'm the Doctor, the Oncoming
      Storm - and you basically meant beat them in a football match, didn't you?
      It's art! A statement on modern society, 'Oh Ain't Modern Society Awful?'!
    </p>
  </aside>
</div>
<!-- /wrap -->
!

CSS 

              
                @import url("https://fonts.googleapis.com/css?family=Bitter:400, 700");

$dark: #252525;
$blue: #263347;
$white: #f6f6f6;
$green: #7db067;
$blueWhite: #edeff4;
$backgroundImage: url(http://f.cl.ly/items/0G3l1S3d0K39232G0p1W/generated.png) 0
  0 repeat;

@mixin hidden {
  display: none;
  visibility: hidden;
}
@mixin visible {
  display: block;
  visibility: visible;
}
@mixin visuallyhidden {
  border: 0;
  clip: rect(0 0 0 0);
  height: 1px;
  width: 1px;
  margin: -1px;
  overflow: hidden;
  padding: 0;
  position: absolute;
}
/*-------------------------------------------------------*/

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

body {
  font: {
    family: "Bitter", sans-serif;
    weight: normal;
    size: 100%;
  }
  line-height: 1.5em;
  color: lighten($dark, 15%);
  background: $dark $backgroundImage;
  text-shadow: 0 -1px 0 rgba(255, 255, 255, 0.5);
}

h1,
h2,
h3,
h4,
h5,
h6 {
  font: {
    family: "Bitter", serif;
    weight: normal;
  }
  color: darken($dark, 7.5%);
}
h1 {
  font-size: 1.5em;
  line-height: 1em;
  margin: 1em 0;
}
h2,
h3 {
  font-size: 1.25em;
  line-height: 1.2em;
  margin: 1.2em 0;
}
h4,
h5,
h6 {
  font-size: 1em;
  line-height: 1.5em;
  margin: 1.5em 0;
}
p {
  margin: 0 0 1.5em 0;
  color: lighten($dark, 30%);
  -webkit-hyphens: auto;
  -moz-hyphens: auto;
  -ms-hyphens: auto;
  -o-hyphens: auto;
  hyphens: auto;
}

a {
  text-decoration: none;
  color: #fff;
  text-shadow: none;
  &:hover {
    border-bottom: 2px solid;
  }
}

#wrap {
  max-width: 960px;
  width: 90%;
  margin: 3em auto;
  background: $blueWhite $backgroundImage;
  overflow: hidden;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

[role="banner"] {
  width: 100%;
  background: $blue $backgroundImage;
  padding: 3em 2.5%;
  & h1 {
    color: #fff;
    text-shadow: none;
    line-height: 1;
    margin: 0;
  }
  & a {
    text-decoration: none;
    color: #fff;
    text-shadow: none;
    &:hover {
      border-bottom: 2px solid;
    }
  }
}

nav {
  height: 2em;
  width: 100%;
  background: $green $backgroundImage;
}

[role="main"] {
  width: 60%;
  float: left;
  z-index: 10;
  background: $white $backgroundImage;
  height: 100%;
  padding: 0 2.5%;
  margin-top: -1.5em;
  border-right: 1px solid lighten($dark, 75%);
  & h1:first-child {
    margin: 2em 0;
  }
  & p:first-of-type {
    color: #000;
  }
}

[role="complimentary"] {
  width: 40%;
  float: right;
  padding: 0 2.5%;
  & p {
    font-size: 0.875em;
    line-height: 1.714286em;
    margin-bottom: 1.714286em;
  }
  & h2 {
    margin: 1.2em 0 2.4em 0;
    & a {
      color: $blue;
      text-decoration: none;
      &:hover {
        border-bottom: 2px solid $blue;
      }
    }
  }
}

input[type="checkbox"] {
  @include visuallyhidden;
}

[for="width_sidebar"] {
  border-right: 1px solid lighten($dark, 75%);
  border-bottom: 1px solid lighten($dark, 75%);
  display: inline;
  border-radius: 0 0 5px 0;
  float: left;
  margin-left: 59.9%;
  position: relative;
  top: 0;
  width: 5%;
  height: auto;
  background: $white $backgroundImage;
  text-align: center;
  color: lighten($dark, 60%);
  line-height: 1.5em;
  &:hover ~ [role="main"] {
    box-shadow: 0 10px 10px rgba(0, 0, 0, 0.1);
  }
  & span {
    &:nth-of-type(1) {
      @include visuallyhidden;
    }
    &:nth-of-type(3) {
      @include hidden;
    }
  }
}

input[type="checkbox"]:checked {
  & ~ [role="complimentary"] {
    width: 100% !important;
    margin-top: 1.2em;
  }
  & ~ [role="main"] {
    width: 100%;
    box-shadow: none;
  }
  & ~ [for="width_sidebar"] {
    border: none;
    margin: 0;
    float: right;
    & span {
      &:nth-of-type(3) {
        @include visible;
      }
      &:nth-of-type(2) {
        @include hidden;
      }
    }
  }
}

@media screen and (max-width: 804px) {
  [for="width_sidebar"] {
    margin-left: 59.7%;
  }
}

@media screen and (max-width: 550px) {
  html {
    font-size: 90%;
  }
  [role="complimentary"] {
    width: 100%;
    background: $blueWhite $backgroundImage;
    margin-top: 1.2em;
  }
  [role="main"] {
    width: 100%;
    margin-top: 0;
  }
  [for="width_sidebar"] {
    @include visuallyhidden;
  }
}
!

JS
!
999px

Console