Web Design in a Nutshell, 3rd Edition

JPEG Decompression

JPEGs need to be decompressed before they can be displayed; therefore, it takes a browser longer to decode and assemble a JPEG than a GIF of the same file size. Bear in mind that a small portion of the download time-savings gained by using a JPEG instead of a GIF is lost to the added time it takes to display. (Not much though, so don’t sweat it.)

JPEGs in AOL Browsers

America Online members generally use some flavor of Internet Explorer for viewing the Web; however, the pages they see have passed through the AOL proxy servers before they reach their browser window.

En route to AOL users, all web page graphics are run through Johnson & Grace compression software for faster downloads. The J&G compression can wreak havoc on image quality and has some particularly sticky issues with JPEGs. Although users can turn off the Use Compressed Graphics option in their Preferences, you can’t count on them to do so. Unfortunately, there’s nothing you can do about it as a developer.