try fixing

src/css/lightbox.css

@@ -61,62 +61,3 @@ img.lightbox {
   text-decoration: none;
   cursor: pointer;
 }
- src/css/site.css 
-+
-1
-−
-0
-@@ -14,4 +14,5 @@
-@import "header.css";
-@import "footer.css";
-@import "highlight.css";
-@import "lightbox.css";
-@import "print.css";
- src/js/06-lightbox.js  0 → 100644
-+
-43
-−
-0
-;(function () {
-  'use strict'
-  var lightbox
-
-  function init () {
-    if (!lightbox) {
-      lightbox = document.createElement('div')
-      lightbox.className = 'modal'
-      lightbox.innerHTML = '<span class="close cursor">&times;</span>\n' +
-        '  <div class="modal-content">\n' +
-        '    <img alt="filled at runtime">\n' +
-        '  </div>'
-
-      var footer = document.getElementsByTagName('footer')[0]
-      footer.parentNode.insertBefore(lightbox, footer.nextSibling)
-
-      lightbox.getElementsByTagName('div')[0].onclick = closeModal
-      lightbox.getElementsByTagName('span')[0].onclick = closeModal
-    }
-  }
-
-  function openModal () {
-    lightbox.style.display = 'block'
-  }
-
-  function closeModal () {
-    lightbox.style.display = 'none'
-  }
-
-  document.querySelectorAll('.imageblock img').forEach(function (element) {
-    if (element.parentNode.nodeName === 'A') {
-      // if parent node is an anchor, keep the anchor instead of opening lightbox
-      return
-    }
-    element.className += ' lightbox'
-    element.addEventListener('click', function (evt) {
-      init()
-      lightbox.getElementsByTagName('img')[0].setAttribute('src', evt.currentTarget.getAttribute('src'))
-      lightbox.getElementsByTagName('img')[0].setAttribute('alt', evt.currentTarget.getAttribute('alt'))
-      openModal()
-    })
-  })
-})()