Drupal Lightbox module

behaviors.js

  /**
   * Subscribe Lightbox
   */

  Drupal.behaviors.dgLightbox = {
    attach: function (context, settings) {
      $('body', context).once('dgLightbox', function () {
        var webform = $('.webform-client-form-271');
        if (webform.length) {
          (webform.children('div')).prepend($("<p class='close-lightbox'>Cancel</p>"));
          $('body').addClass('lightbox');
          $('.close-lightbox').click(function(){
            location.reload();
          });
        }
      });
    }
  };

lightbox.module

<?php

/**
 * @file
 * A module to render a webform lightbox
 */

function breezes_lightbox_help($path, $arg) {
  switch ($path) {
	case "admin/help#breezes_lightbox":
	  return '' . t("This is the help text for the breezes lightbox") . '';
	  break;
  }
}

function breezes_lightbox_page_build(&$page) {
  $block = module_invoke('webform', 'block_view', 'client-block-271');
  if(!isset($_COOKIE['lightbox'])){
	echo('no cookie - setting');
	setcookie('lightbox', 1, 0);
	print render($block['content']);
  } else {
	echo('we have a cookie!');
  }
}

lightbox.scss

// Subscribe lightbox styles

.webform-client-form-271 {
  position: absolute;
  width: 500px;
  height: 500px;
  z-index: 10001;
  left: 50%;
  top: 50%;
  transform: translateX(-50%) translateY(-50%);

  > div {
    background: #cccccc;
    padding: 2em;
  }

  .close-lightbox {
    @include fontello-replace-with-icon($icon-cancel);
    position: absolute;
    top: 0;
    right: 0;
    cursor: pointer;
    z-index: 10001;
  }
}


body.lightbox:before {
  content: '';
  position: absolute;
  height: 100%;
  width: 100%;
  background:rgba(0,0,0,0.5);
  top: 0;
  z-index: 10000;
}