DIRECTION The next line is the first that gets cut and pasted for test.html
<!DOCTYPE html>
<html>
<meta charset="utf=8">
<head>
<link rel="stylesheet" type="text/css" href="popdown.css">
<style type="style/css">
</style>
<script src="EDIT THIS to point to URL of popdown.js"></script>
<title>Test Serving Images</title>
</head>
<body>

<div style="text-align: center;">
<h1>Testing an image server<br> </h1>
</div>

TO BE REMOVED This comment points out that the  next few lines need to be within
TO BE REMOVED the body of each page using the image server.
<!-- The Modal -->
<div id="myModal" class="modal">
  <span class="close">&times;</span>
  <img class="modal-content" id="img01">
  <div id="caption"> </div>
</div>

<a href='javascript:popdown("EDIT THIS to point to URL of image", "Title
appearing below picture")'>Click-this-anchor-to-see-image</a>

</body> </html>
DIRECTION line above is the last to be cut and pasted for test.html
DIRECTION line below is the first to be cut and pasted for popdown.css
#myImg {
  border-radius: 5px;
  cursor: pointer;
  transition: 0.3s;
}
#myImg:hover {opacity: 0.7;}

/* The Modal (background) */
.modal {
  display: none; /* Hidden by default */
  position: fixed; /* Stay in place */
  z-index: 1; /* Sit on top */
  padding-top: 100px; /* Location of the box */
  left: 0;
  top: 0;
  width: 100%; /* Full width */
  height: 100%; /* Full height */
  overflow: auto; /* Enable scroll if needed */
  background-color: rgb(0,0,0); /* Fallback color */
  background-color: rgba(0,0,0,0.9); /* Black w/ opacity */
}

/* Modal Content (image) */
.modal-content {
  margin: auto;
  display: block;
  width: 80%;
  max-width: 700px;
}

/* Caption of Modal Image */
#caption {
  margin: auto;
  display: block;
  width: 80%;
  max-width: 700px;
  text-align: center;
  color: #ccc;
  padding: 10px 0;
  height: 150px;
}

/* Add Animation */
.modal-content, #caption {  
  -webkit-animation-name: zoom;
  -webkit-animation-duration: 0.6s;
  animation-name: zoom;
  animation-duration: 0.6s;
}

@-webkit-keyframes zoom {
  from {-webkit-transform:scale(0)} 
  to {-webkit-transform:scale(1)}
}

@keyframes zoom {
  from {transform:scale(0)} 
  to {transform:scale(1)}
}

/* The Close Button */
.close {
  position: absolute;
  top: 15px;
  right: 35px;
  color: #f1f1f1;
  font-size: 40px;
  font-weight: bold;
  transition: 0.3s;
}

.close:hover,
.close:focus {
  color: #bbb;
  text-decoration: none;
  cursor: pointer;
}

/* 100% Image Width on Smaller Screens */
@media only screen and (max-width: 700px){
  .modal-content {
    width: 100%;
  }
DIRECTION line above is the last to be cut and pasted for popdown.css
DIRECTION line below is the first to be cut and pasted for popdown.js
function popdown(image, ttext)
{
// Get the modal
var modal = document.getElementById("myModal");

// Get the image and insert it inside the modal - use its "alt" text as a caption
var img = image;
var modalImg = document.getElementById("img01");
var captionText = document.getElementById("caption");
    modal.style.display = "block";
    modalImg.src = image;
    captionText.innerHTML=ttext;

// Get the <span> element that closes the modal
var span = document.getElementsByClassName("close")[0];

// When the user clicks on <span> (x), close the modal
span.onclick = function() { 
  modal.style.display = "none";
}
}
DIRECTION line above is the last to be cut and pasted for popdown.js