Reduce the size of PNG images to optimize your website
Optipng is a free program that is very easy to use. It only reduces the size of PNG file, without losing quality of the image.
Most designers want to use PNG file format to remove a background from images that the use of a compressed file like a JPEG will not do. This video will show you how to place it on your computer, as it does not have an install. The program also is run with the command line, so I show you some of the basic command line feature.
Optipng may be downloaded from http://www.optipng.sourceforge.net/