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HTML 

              
                <div class="page grid">
  <header class="grid">
    <h1 class="span-5-8">Fluid Layout Preview</h1>
    <p class="span-3-8"><a href="http://justifygrid.com">Justify Grid</a></p>
  </header>
  <img class="span-5-8 push-3-8" src="http://justifygrid.com/images/customize.png" alt=""/>
  <form id="builder" class="span-3-8 pull-5-8">
    <label><span>Number of columns</span> <input type="text" name="columns" value="12" /></label>
    <label><span>Column width (em)</span> <input type="text" name="column"  value="4"  /></label>
    <label><span>Gutter width (em)</span> <input type="text" name="gutter"  value="2.5"/></label>
    <button class="btn" type="submit">Preview!</button>
  </form>
</div>
<div id="preview">
  <p class="learn-more">Learn more about <a href="http://justifygrid.com">Justify Grid</a></p>
</div>
!

CSS 

              
                html, body {
  padding: 0;
  margin: 0;
  color: #fff;
  font: 300 100%/1.5 'Open Sans', sans-serif;
}
html {
  min-height: 100%;
  background-color: #8495a5;
  background-image:
    -webkit-linear-gradient(top, rgba(181,191,201,0.5), rgba(79,89,99,0.5)),
    -webkit-radial-gradient(center top, rgba(132,149,165,0.6), #8495a5 80%),
    -webkit-linear-gradient(top, #ffffff 1px, transparent 1px),
    -webkit-linear-gradient(left, #ffffff 1px, transparent 1px);
  background-image:
    -moz-linear-gradient(top, rgba(181,191,201,0.5), rgba(79,89,99,0.5)),
    -moz-radial-gradient(center top, rgba(132,149,165,0.6), #8495a5 80%),
    -moz-linear-gradient(top, #ffffff 1px, transparent 1px),
    -moz-linear-gradient(left, #ffffff 1px, transparent 1px);
  background-image:
    -o-linear-gradient(top, rgba(181,191,201,0.5), rgba(79,89,99,0.5)),
    -o-radial-gradient(center top, rgba(132,149,165,0.6), #8495a5 80%),
    -o-linear-gradient(top, #ffffff 1px, transparent 1px),
    -o-linear-gradient(left, #ffffff 1px, transparent 1px);
  background-image:
    linear-gradient(to bottom, rgba(181,191,201,0.5), rgba(79,89,99,0.5)),
    radial-gradient(at center top, rgba(132,149,165,0.6), #8495a5 80%),
    linear-gradient(to bottom, #ffffff 1px, transparent 1px),
    linear-gradient(to right, #ffffff 1px, transparent 1px);
  background-attachment: fixed;
  background-size: auto, auto, 1em 1em, 1em 1em;
  background-position: 0 -1px;
}
body {
  margin: 0 1em;
}


.page, .learn-more {
  max-width: 49.5rem;
  margin: 0 auto;
}
.page > header > h1, .page > header > p {
  margin: 0;
  color: #fff;
  font: 700 1.5rem/1.3 'Josefin Slab', serif;
  text-shadow: 0.05em 0.05em 0.1em rgba(0, 0, 0, 0.4);
}
.page > header > p {
  text-align: right;
}
.page > header > p a {
  text-decoration: none;
}


.btn {
  display: inline-block;
  padding: 0.4em 1em;
  border: 0;
  margin: 1em 0;
  border-radius: 0.25em;
  background-color: #8495a5;
  background-image: -webkit-linear-gradient(top, #9caab7, #697784);
  background-image:    -moz-linear-gradient(top, #9caab7, #697784);
  background-image:      -o-linear-gradient(top, #9caab7, #697784);
  background-image:   linear-gradient(to bottom, #9caab7, #697784);
  color: #fff;
  font-size: 1.25em;
  font-weight: 400;
  text-align: center;
  text-decoration: none;
}
.btn:focus, .btn:hover {
  box-shadow:
    inset 0 0 0.5em rgba(255, 255, 255, 0.5),
    0.1em 0.1em 0.2em rgba(0, 0, 0, 0.25);
}
.btn:active {
  box-shadow:
    inset 0 0 0.5em rgba(255, 255, 255, 0.5),
    0.05em 0.05em 0.1em rgba(0, 0, 0, 0.25);
}


#builder {
  margin: 0;
  text-align: center;
}


a {
  color: #fff;
}
img {
  display: block;
  width: 100%;
}
label > span, input, button {
  box-sizing: border-box;
}
label {
  display: block;
  margin: 0 0 0.25em;
  text-align: left;
}
input, button {
  vertical-align: baseline;
  padding: 0.25em;
  border: none;
  margin: 0;
  color: #fff;
  font: 300 100%/1.2 'Open Sans', sans-serif;
}
input[type="text"] {
  width: 100%;
  border: 1px solid #ccc;
  color: #333;
}
button {
  -webkit-appearance: none;
  cursor: pointer;
}


::-moz-selection {
  background: #8495a5;
  color: #fff;
  text-shadow: none;
}
::selection {
  background: #8495a5;
  color: #fff;
  text-shadow: none;
}


/* Justify Grid's base CSS */
.grid {
  text-align: justify !important;
  text-justify: distribute-all-lines;
  font-size: 0 !important;
}
.grid:after {
  content: "";
  display: inline-block;
  width: 100%;
}
.grid > * {
  vertical-align: top;
  display: inline-block;
  width: 100%;
  text-align: left;
  font-size: medium;
}
[class*="push-"], [class*="pull-"] {
  position: relative;
}


@media screen and (min-width: 30em) {
  /* Nested grids not available in this demo */
  .span-3-8 { width: 34.34343%; }
  .span-5-8 { width: 60.60606%; }
  .push-3-8 { left:  39.39394%; }
  .pull-5-8 { left: -65.65657%; }

  .page > header > h1, .page > header > p {
    font-size: 1.75rem;
  }
  img {
    margin-top: 1.5em;
  }
}
@media screen and (min-width: 48em) {
  .page > header > h1, .page > header > p {
    font-size: 2.5rem;
  }
}
!

JS 

              
                /*
 * Download your customized CSS at:
 * http://justifygrid.com/#customize
 * including push, pull, prepend and append classes
 *
 * Created by:
 * https://twitter.com/CrocoDillon
 *
 * Original JS at:
 * http://justifygrid.com/js/builder.js
 */

(function(d){
  var   form          = d.forms.builder,
        outputElement = d.getElementById('preview'),
        outputHtml;

  form.onsubmit = function(e) {
    e = e || event;
    (e.preventDefault) ? e.preventDefault() : e.returnValue = false;

    var i,
        n           = parseInt(form.columns.value),
        columnWidth = parseFloat(form.column.value),
        gutterWidth = parseFloat(form.gutter.value),
        totalWidth  = n * columnWidth + (n - 1) * gutterWidth;

    if (n < 1 ||
        columnWidth <= 0 ||
        gutterWidth <= 0) {
      outputElement.innerHTML = '<p style="text-align:center">Awww... you broke the grid!  (╯°□°)╯  ┻┻</p>';
      return;
    }

    function generateSpan(span) {
      var width = 100 * (span * columnWidth + (span - 1) * gutterWidth) / totalWidth;
      width = width.toFixed(6).replace(/\.?0+$/, '');
      
      return '<div style="width:' + width + '%;margin-bottom:1em;background:#a7cd80;white-space:pre">&nbsp;.span-' + span + '</div>';
    }
    
    outputHtml = '<div class="grid" style="overflow-x:hidden;max-width:' + totalWidth + 'rem;margin:0 auto;color:#333;font-family:Consolas, Monaco, \'Andale Mono\', monospace;line-height:3">';
    
    // first line of inline-blocks, each spans 1 column
    for (i = 1; i <= n; i++) {
      outputHtml += generateSpan(1) + ' ';
    }
    // other lines, each with 2 inline-blocks of every possible span
    i = n - 1;
    while(i >= n / 2) {
      outputHtml += generateSpan(i) + ' ';
      outputHtml += generateSpan(n - i) + ' ';
      i--;
    }
    
    outputHtml += '</div>';

    form.columns.value = n;
    form.column.value  = columnWidth;
    form.gutter.value  = gutterWidth;

    outputElement.innerHTML = outputHtml;
  }
})(document);
!
999px

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