Lazy loader for image. Don't need an external library Don't need to modify your HTML to change the attribute of your images SEO friendly
- the default image to display before to load the true one
- A custom_offset to load the true image before it enter in viewport, to avoid user to wait the download
<script> lazyImg.setConfig('img/loading.gif', 400); </script>
This script is used on this website Tuto&Co and more explanation in French here