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by Dean Marsden on 4th July 2011
If you’ve ever run a website through Google’s Page Speed tool you might have received a recommendation to ‘Combine images into CSS Sprites’. Firstly what is a CSS sprite? A cocktail made from a popular fizzy drink? No. A rather ugly looking website image file? Yes!
Before I explain how it works, you probably want to know why Google is recommending you use on or if you have a high traffic website, how it can help you save money. Converting many of your images into one CSS Sprite will reduce the load time of your website quite significantly. This has two beneficial effects:
Every time a user visits your website, their computer makes requests to download every image used on your web page. This back and forth can really slow down the speed in which your web page loads. CSS Sprites work by combining many graphics into one image file thus reducing the number of requests each visitor has to make to your website’s hosting. The file size of one image is typically less (although not always) than the combined size of all the separate images due to the way jpeg or gif files are compressed.
I only recommend creating a CSS Sprite for smaller image files such as icons, navigation/menu graphics and repeating background images. It will not benefit you to create them for large graphics and photographs.
A CSS Sprite will look a little odd after creation, a bit like a sticker sheet, but with clever positioning in your CSS stylesheet nobody will ever know of its ugliness. You simply set the top and left position and width and height of the graphic you wish to show in each stylesheet ID or class. Its a bit like your cropping the image from the image sprite using the coordinates of its position and size.
Websites such as Facebook, Google and Amazon use CSS Sprites to make huge savings on their hosting costs and deliver a fast site to each user. In fact for every second slower Amazon’s site loads, they could lose hundreds or even thousands of sales. Let’s look at Amazon’s image sprite:
If you wish to create a image for a CSS Sprite you can do it manually in any most image editing tools such as Adobe Photoshop. There is also a website called SpriteMe which allows you to enter the URL of your website and it will identify all the images used and it will create a single file of the smaller images and you can also choose which images you want to combine then download the created image for use in your new CSS Sprite. The other step of the process requires good knowledge of CSS code. You may need to get a professional website designer to create this for you.
Why not try making your own CSS Sprites. You can drastically improve your website for both users and search engines in one hit.