CSS background image hacks

Emulating background image crop, background image opacity, background transforms, and improved background positioning. A few hacks relying on CSS pseudo-elements to emulate features unavailable or not yet widely supported by modern browsers.
Demos: Example CSS background image hacks
Pseudo-element hacks can fill some gaps in existing browser support for CSS features, without resorting to presentational HTML. In some cases, they even make it possible to emulate things that are not currently part of any W3C working draft, like background transforms and background image opacity.
Most of the hacks in this article tie in with the pseudo-element hack described in an earlier article – Multiple Backgrounds and Borders with CSS 2.1. That article already describes how to emulate multiple background support and its demo page shows several other uses of the basic principle. This article presents a few of those effects and applications in greater detail.

http://nicolasgallagher.com/css-background-image-hacks/