Inspect Element has written a tutorial to show us you can create a simple “stacked” look to some images with CSS3 Pseudo-Elements.
It’s important to note that currently only Firefox supports transitions on :before and :after (the transitions are defined earlier in the page on the pseudo elements themselves) as far as I know. WebKit doesn’t seem to support it in any incarnation at this point but hopefully will add it sometime soon.
Requirements: CSS3 Pseudo-Elements
License: License Free