All “lightbox scripts” have the image gallery option which are built like this:
<a class="grouped_elements" rel="group1" href="image_big_1.jpg"><img src="image_small_1.jpg" alt=""/></a>
<a class="grouped_elements" rel="group1" href="image_big_2.jpg"><img src="image_small_2.jpg" alt=""/></a>
Take for example the fancybox plugin and look at the image galleries, there are 3 thumbnails for those 3 images in the gallery, my question is how to add those 3 images in the lightbox in only one thumbnail?
Only put one img tag. So for all but the first a href you have nothing in-between.