IMAGE OPTIMIZING

 

GIF - Is good for icons and logos, something that is flat and simple with solid colours, this is because the maximum amount of colours in a GIF image is 256. Hasn't got great quality

 

JPEG - This is used for anything with a gradient, mostly photos are used in this format because of the amount of colours it holds, millions. Has really high quality.

 

PNG - This is Fireworks native image. It can have transparent, therefore able to have other shapes such as a circle, rather than just the standard square. This quality is inbetween GIF and JPEG.