Optimise Images and Use CSS Sprites

Another way to improve the performance of your PrestaShop website is to optimise your images.  All images that use about 256 colours or less should be saved in PNG-8 format using an image editor like Paint.NET.  PNG-8 is the successor to GIF and provides the same lossless compression in a smaller size.  Images with many more than 256 colours should be saved in JPEG format.  JPEG uses lossy compression rather than lossless compression like PNG, so keep a copy of the original image in PNG-24 format before compressing it.  When compressing images as JPEGs, try to reduce the quality percentage as much as possible, but not so much that the compression is noticeable.

Try to keep the size of each image under 25 KB, since that is the maximum size mobile phone devices like iPhones will cache.  Also, make sure your favicon is small, preferably less than 1 KB, so that it loads quickly.  You can use an icon editor like IcoFX to create an icon.  Upload the icon on the Preferences > Appearance tab.

Images referenced in CSS files can be combined into CSS sprites to reduce the file size of the images and the number of HTTP image requests.  SpriteMe is a tool that will do this automatically and report how much download can be saved before applying it to your site.