The box-shadow CSS property describes one or more shadow effects as a comma-separated list. It allows casting a drop shadow from the frame of almost any element. If a border-radius is specified on the element with a box shadow, the box shadow takes on the same rounded corners. The z-ordering of multiple box shadows is the same as multiple text shadows (the first specified shadow is on top).

[Webplatform](docs.webplatform.org/wiki/css/properties/box-shadow "Webplatform")
[Mozilla docs](https://developer.mozilla.org/en-US/docs/Web/CSS/box-shadow "Mozilla")
[Caniuse](http://caniuse.com/#feat=box-shadow "Caniuse")