W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<style>
/* The Image Box */
div.img {
  border: 1px solid #ccc;
}

div.img:hover {
  border: 1px solid #777;
}

/* The Image */
div.img img {
  width: 100%;
  height: auto;
  cursor: pointer;
}

/* Description of Image */
div.desc {
  padding: 15px;
  text-align: center;
}

* {
  box-sizing: border-box;
}

/* Add Responsiveness */
.responsive {
  padding: 0 6px;
  float: left;
  width: 24.99999%;
}

/* 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 {transform:scale(0)} 
  to {transform:scale(1)}
}

@keyframes zoom {
  from {transform:scale(0.1)} 
  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;
}

/* Responsive Columns */
@media only screen and (max-width: 700px){
  .responsive {
    width: 49.99999%;
    margin: 6px 0;
  }
  .modal-content {
    width: 100%;
  }
}

@media only screen and (max-width: 500px){
  .responsive {
    width: 100%;
  }
}

/* Clear Floats */
.clearfix:after {
  content: "";
  display: table;
  clear: both;
}
</style>
</head>
<body>

<h2 style="text-align:center">Advanced Image Gallery</h2>

<div class="responsive">
  <div class="img">
    <img src="img_5terre.jpg" alt="Cinque Terre" width="300" height="200">
    <div class="desc">Cinque Terre</div>
  </div>
</div>

<div class="responsive">
  <div class="img">
    <img src="img_forest.jpg" alt="Forest" width="300" height="200">
    <div class="desc">Forest Bridge</div>
  </div>
</div>

<div class="responsive">
  <div class="img">
    <img src="img_lights.jpg" alt="Northern Lights" width="300" height="200">
    <div class="desc">Northern Lights, Norway</div>
  </div>
</div>

<div class="responsive">
  <div class="img">
    <img src="img_mountains.jpg" alt="Mountains" width="300" height="200">
    <div class="desc">Beautiful Mountains</div>
  </div>
</div>

<div id="myModal" class="modal">
  <span class="close">×</span>
  <img class="modal-content" id="img01">
  <div id="caption"></div>
</div>

// 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";
}

// Get all images and insert the clicked image inside the modal
// Get the content of the image description and insert it inside the modal image caption
var images = document.getElementsByTagName('img');
var modalImg = document.getElementById("img01");
var captionText = document.getElementById("caption");
var i;
for (i = 0; i < images.length; i++) {
  images[i].onclick = function(){
    modal.style.display = "block";
    modalImg.src = this.src;
    modalImg.alt = this.alt;
    captionText.innerHTML = this.nextElementSibling.innerHTML;
  }
}
</script>

<div style="padding:6px;">
  <p>This example combines CSS (animation and media queries) and JavaScript, to create a responsive image gallery that will enlarge an image when it is clicked on.</p>
</div>

</body>
</html>

​x
 
<!DOCTYPE html><html><head><style>/* The Image Box */div.img {  border: 1px solid #ccc;}​div.img:hover {  border: 1px solid #777;}​/* The Image */div.img img {  width: 100%;  height: auto;  cursor: pointer;}​/* Description of Image */div.desc {  padding: 15px;  text-align: center;}​* {  box-sizing: border-box;}​/* Add Responsiveness */.responsive {  padding: 0 6px;  float: left;  width: 24.99999%;}​/* 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 */