CSS sprites are a way to reduce the number of HTTP requests made for image resources referenced by your site. Images are combined into one larger image at defined X and Y coorindates. Having assigned this generated image to relevant page elements the background-position CSS property can then used to shift the visible area to the required component image.
another way to save precious HTTP hits from your page
We describe our investigation of the effect of persistent connections, pipelining and link level document compression on our client and server HTTP implementations.