Images make up the single largest resource most websites pull from their server to load to the browser. While images do make for a vibrant and attractive design, the more images that are pulled the longer it takes for a page to respond.A way to lessen then impact of all these images being pulled is to ensure the images are compressed.Non-compressed images should be compressed to save on the site overhead when loading.
Image compression is minimizing the size in bytes of a graphics file without degrading the quality of the image to an unacceptable level. The reduction in file size allows more images to be stored in a given amount of disk or memory space. … There are several different ways in which image files can be compressed.
Image compression should happen in either in image editing software or using a third party tool (a list of which can be found here http://codefusionlab.blogspot.com/2009/07/16-impressive-image-optimization-tools.html)