Yahoo! YSlow Smush.it™ uses optimization techniques specific to image format to remove unnecessary bytes from image files. It will reduce the load time for your website without changing their look or visual quality of your images.
Background images add a custom touch to websites, but can impact performance. Combining multiple images into sprites can add zip to your site’s load time. There is a constantly growing and improving collection of online tools to make sprite creation and use quick and easy.