Dithering: Good, Bad, and Ugly
http://style.cleverchimp.com/dithering/

Fahrner, Todd
Cleverchimp
1997

Abstract:

This piece discusses dithering in the context of Web graphics, and introduces the WebScrub image optimization algorithm developed by Todd Fahrner at Verso, realized as freely-downloadable Photoshop plug-ins for Mac and Windows, as well as scripts for the image-processing program DeBabelizer (MacOS only at present).