CSS sprite, as interesting as it is called, is also an interesting CSS method itself. This approach involves changing an image to another different image, or the same image but different colour scape (greyscale, sephia etc.) upon hover.
The advantage of using the using CSS sprite technique is that the web page will automatically load all images at once, instead of one by one. This will speed up the loading time and there will be not much delay for users with slow Internet connection.
Tutorial By Sani Halid