title: Gray out the Background Making only Popup Visible
body: <p>I want to have a popup where all the background is grayed out but I am not sure how to do it.</p>
  
  <p>I found this on codepen (<a href="http://bit.ly/1NDe103" rel="nofollow">http://codepen.io/adventuresinmissions/pen/nrhHF</a>) that does this (grays out the background when popup is opened). What makes it do that and how can I reproduce this?</p>
  
  <p>I beleive it is somewhere in the css:</p>
  
  <pre><code>/* http://meyerweb.com/eric/tools/css/reset/ 
     v2.0 | 20110126
     License: none (public domain)
  */
  
  html, body, div, span, applet, object, iframe,
  h1, h2, h3, h4, h5, h6, p, blockquote, pre,
  a, abbr, acronym, address, big, cite, code,
  del, dfn, em, img, ins, kbd, q, s, samp,
  small, strike, strong, sub, sup, tt, var,
  b, u, i, center,
  dl, dt, dd, ol, ul, li,
  fieldset, form, label, legend,
  table, caption, tbody, tfoot, thead, tr, th, td,
  article, aside, canvas, details, embed, 
  figure, figcaption, footer, header, hgroup, 
  menu, nav, output, ruby, section, summary,
  time, mark, audio, video {
      margin: 0;
      padding: 0;
      border: 0;
      font-size: 100%;
      font: inherit;
      vertical-align: baseline;
  }
  /* HTML5 display-role reset for older browsers */
  article, aside, details, figcaption, figure, 
  footer, header, hgroup, menu, nav, section, main {
      display: block;
  }
  body {
      line-height: 1;
  }
  ol, ul {
      list-style: none;
  }
  blockquote, q {
      quotes: none;
  }
  blockquote:before, blockquote:after,
  q:before, q:after {
      content: '';
      content: none;
  }
  table {
      border-collapse: collapse;
      border-spacing: 0;
  }
  /* -------------------------------- 
  
  Primary style
  
  -------------------------------- */
  html * {
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
  }
  
  *, *:after, *:before {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
  }
  
  body {
    font-size: 100%;
    font-family: "Lato", sans-serif;
    color: #8f9cb5;
    background-color: #ffd88f;
  }
  
  a {
    color: #35a785;
    text-decoration: none;
  }
  
  /* -------------------------------- 
  
  Modules - reusable parts of our design
  
  -------------------------------- */
  .img-replace {
    /* replace text with an image */
    display: inline-block;
    overflow: hidden;
    text-indent: 100%;
    color: transparent;
    white-space: nowrap;
  }
  
  /* -------------------------------- 
  
  xnugget info 
  
  -------------------------------- */
  .cd-nugget-info {
    text-align: center;
    position: absolute;
    width: 100%;
    height: 50px;
    line-height: 50px;
    bottom: 0;
    left: 0;
  }
  .cd-nugget-info a {
    position: relative;
    font-size: 14px;
    color: #5e6e8d;
    -webkit-transition: all 0.2s;
    -moz-transition: all 0.2s;
    transition: all 0.2s;
  }
  .no-touch .cd-nugget-info a:hover {
    opacity: .8;
  }
  .cd-nugget-info span {
    vertical-align: middle;
    display: inline-block;
  }
  .cd-nugget-info span svg {
    display: block;
  }
  .cd-nugget-info .cd-nugget-info-arrow {
    fill: #5e6e8d;
  }
  
  /* -------------------------------- 
  
  Main components 
  
  -------------------------------- */
  header {
    height: 200px;
    line-height: 200px;
    text-align: center;
    background-color: #5e6e8d;
    color: #FFF;
  }
  header h1 {
    font-size: 20px;
    font-size: 1.25rem;
  }
  
  .cd-popup-trigger {
    display: block;
    width: 170px;
    height: 50px;
    line-height: 50px;
    margin: 3em auto;
    text-align: center;
    color: #FFF;
    font-size: 14px;
    font-size: 0.875rem;
    font-weight: bold;
    text-transform: uppercase;
    border-radius: 50em;
    background: #35a785;
    box-shadow: 0 3px 0 rgba(0, 0, 0, 0.07);
  }
  @media only screen and (min-width: 1170px) {
    .cd-popup-trigger {
      margin: 6em auto;
    }
  }
  
  /* -------------------------------- 
  
  xpopup 
  
  -------------------------------- */
  .cd-popup {
    position: fixed;
    left: 0;
    top: 0;
    height: 100%;
    width: 100%;
    background-color: rgba(94, 110, 141, 0.9);
    opacity: 0;
    visibility: hidden;
    -webkit-transition: opacity 0.3s 0s, visibility 0s 0.3s;
    -moz-transition: opacity 0.3s 0s, visibility 0s 0.3s;
    transition: opacity 0.3s 0s, visibility 0s 0.3s;
  }
  .cd-popup.is-visible {
    opacity: 1;
    visibility: visible;
    -webkit-transition: opacity 0.3s 0s, visibility 0s 0s;
    -moz-transition: opacity 0.3s 0s, visibility 0s 0s;
    transition: opacity 0.3s 0s, visibility 0s 0s;
  }
  
  .cd-popup-container {
    position: relative;
    width: 90%;
    max-width: 400px;
    margin: 4em auto;
    background: #FFF;
    border-radius: .25em .25em .4em .4em;
    text-align: center;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.2);
    -webkit-transform: translateY(-40px);
    -moz-transform: translateY(-40px);
    -ms-transform: translateY(-40px);
    -o-transform: translateY(-40px);
    transform: translateY(-40px);
    /* Force Hardware Acceleration in WebKit */
    -webkit-backface-visibility: hidden;
    -webkit-transition-property: -webkit-transform;
    -moz-transition-property: -moz-transform;
    transition-property: transform;
    -webkit-transition-duration: 0.3s;
    -moz-transition-duration: 0.3s;
    transition-duration: 0.3s;
  }
  .cd-popup-container p {
    padding: 3em 1em;
  }
  .cd-popup-container .cd-buttons:after {
    content: "";
    display: table;
    clear: both;
  }
  .cd-popup-container .cd-buttons li {
    float: left;
    width: 50%;
    list-style: none;
  }
  .cd-popup-container .cd-buttons a {
    display: block;
    height: 60px;
    line-height: 60px;
    text-transform: uppercase;
    color: #FFF;
    -webkit-transition: background-color 0.2s;
    -moz-transition: background-color 0.2s;
    transition: background-color 0.2s;
  }
  .cd-popup-container .cd-buttons li:first-child a {
    background: #fc7169;
    border-radius: 0 0 0 .25em;
  }
  .no-touch .cd-popup-container .cd-buttons li:first-child a:hover {
    background-color: #fc8982;
  }
  .cd-popup-container .cd-buttons li:last-child a {
    background: #b6bece;
    border-radius: 0 0 .25em 0;
  }
  .no-touch .cd-popup-container .cd-buttons li:last-child a:hover {
    background-color: #c5ccd8;
  }
  .cd-popup-container .cd-popup-close {
    position: absolute;
    top: 8px;
    right: 8px;
    width: 30px;
    height: 30px;
  }
  .cd-popup-container .cd-popup-close::before, .cd-popup-container .cd-popup-close::after {
    content: '';
    position: absolute;
    top: 12px;
    width: 14px;
    height: 3px;
    background-color: #8f9cb5;
  }
  .cd-popup-container .cd-popup-close::before {
    -webkit-transform: rotate(45deg);
    -moz-transform: rotate(45deg);
    -ms-transform: rotate(45deg);
    -o-transform: rotate(45deg);
    transform: rotate(45deg);
    left: 8px;
  }
  .cd-popup-container .cd-popup-close::after {
    -webkit-transform: rotate(-45deg);
    -moz-transform: rotate(-45deg);
    -ms-transform: rotate(-45deg);
    -o-transform: rotate(-45deg);
    transform: rotate(-45deg);
    right: 8px;
  }
  .is-visible .cd-popup-container {
    -webkit-transform: translateY(0);
    -moz-transform: translateY(0);
    -ms-transform: translateY(0);
    -o-transform: translateY(0);
    transform: translateY(0);
  }
  @media only screen and (min-width: 1170px) {
    .cd-popup-container {
      margin: 8em auto;
    }
  }
  </code></pre>
  
  <p>Or in the JS:</p>
  
  <pre><code>jQuery(document).ready(function($){
      //open popup
      $('.cd-popup-trigger').on('click', function(event){
          event.preventDefault();
          $('.cd-popup').addClass('is-visible');
      });
  
      //close popup
      $('.cd-popup').on('click', function(event){
          if( $(event.target).is('.cd-popup-close') || $(event.target).is('.cd-popup') ) {
              event.preventDefault();
              $(this).removeClass('is-visible');
          }
      });
      //close popup when clicking the esc keyboard button
      $(document).keyup(function(event){
          if(event.which=='27'){
              $('.cd-popup').removeClass('is-visible');
          }
      });
  });
  </code></pre>
  
  <p>Thank you.</p>
  
  <p>Let me know if I wasn't clear enough.</p>