One way of speeding up a website is to minimize the number of http requests by combining several small files of the same type. You can do this with scripts, stylesheets, and–by combining images into sprites–with icons and other pictures. So far so good. But using sprites and @media queries gets tricky when addressing devices with a high density display (such as Retina in iOS).
Important update as of 2016-01: HTTP/2 makes sprites obsolete. You should no longer be using this technique! (This article is only of historical value.) [Read more…]