we'll show you how to create a simple ‘stacked’ look to some images.

The HTML

<div class="stack">
    <img src="image1.jpg" />
</div>

Unfortunately WebKit generated content isn’t supported on the img element currently so we have to wrap a div around it to get it to work. It may work in the future as noted in the spec:

Note. This specification does not fully define the interaction of :before and :after with replaced elements (such as IMG in HTML). This will be defined in more detail in a future specification.

The CSS

.stack { position: relative; z-index: 10; }
 
/* Image styles */
.stack img { max-width: 100%; height: auto; vertical-align: bottom; border: 10px solid #fff; border-radius: 3px;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    -webkit-box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
    -moz-box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
}
 
/* Stacks creted by the use of generated content */
.stack:before, .stack:after { content: ""; border-radius: 3px; width: 100%; height: 100%; position: absolute; border: 10px solid #fff; left: 0;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    -webkit-box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
    -moz-box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
    -webkit-transition: 0.3s all ease-out;
    -moz-transition: 0.3s all ease-out;
    transition: 0.3s all ease-out;
}
.stack:before { top: 4px; z-index: -10; } /* 1st element in stack (behind image) */
.stack:after { top: 8px; z-index: -20; } /* 2nd element in stack (behind image) */

Read more:http://inspectelement.com/tutorials/create-the-illusion-of-stacked-elements-with-css3-pseudo-elements/