These days it must use the CSS Sprite technique, this is the best technique to reduce image load on a particular site (means reducing the page load too). Because each image is an extra HTTP request.
There’s is always a solution or another alternative to overcome the problem, so combining background images into a CSS sprite would be a good idea to reduce the load on-page. But creating sprites manually is very hard and time-consuming, requiring arcane knowledge and lots of trial and error. SpriteMe removes the hassles with the click of a button.
There are many easy and quick manual techniques to create your own CSS Sprites, but I am sure there are some folks for whom time is money, then you are good to go with this easy tool to generate CSS Sprites in no time and with a little knowledge of CSS.
Installation is very simple go-to SpriteMe and dragging the “SpriteMe drag this link!” link to your bookmark toolbar or right-click to add it to your favorites. Using it is also simple, go to any URL or page and then click on the bookmarked SpriteMe link, then it immediately grabs the images and CSS Sprites used in that particular page as shown in the snapshot above. In the same window, you have many buttons to create either new sprite or make sprite and after you are done with it it just injects the sprite into your current page, of course, you have always had an option to save the changes and implement the same in your current website.
Hope you will find this tool useful, share your thoughts about the tool or share your experience with any other CSS Sprite techniques you found interesting.