*sigh*
ok lets go forth and explain.
interlaced and non-interlaced gifs are of the same quality. the difference is in the
loading appearance.
interlaced gifs load in phases of quality.. starting from a very low quality ( fuzzy ) to higher quality until the gif is fully loaded. this loading effect is visible as the browser gets more and more info from the web server.
non-interlaced gifs load directly.. which means that the browser displays the gif line by line, from top to bottom as the gif loads.
the advantage of using interlaced gifs(esp with large gifs or on slow connections) is that the user will see something on his/her screen while the gif downloads. this doesn't mean that the gif loads faster or with lesser color (an interlaced gif with 16 colors has the same amount of colors of a non-interlaced gif with 16 colors). it just means that the gif will load in phases of quality.. thereby giving the user something to look at (thereby lessening the chance of the user thinking that the page is not loading and therefore leaving the page for example) while the page loads.
for an example of an interlaced gif take a look @
http://m.antitrend.net . the splash gif is interlaced and it will load in phases of quality.
<---- the following is taken from
http://www.med.yale.edu/caim/manual/...gif_files.html --->
"The conventional (non-interlaced) GIF graphic downloads one line of pixels at a time, and Web viewers like Netscape display each line of the image as it gradually builds on the screen. In interlaced GIF files the image data is stored in a format that allows Netscape (and other viewers that support interlaced GIFs) to begin to build a low-resolution version of the full-sized GIF picture on the screen while the file is still downloading. The "fuzzy-to-sharp" animated effect of interlacing is visually appealing, but the most important benefit of interlacing is that it gives the reader a quick preview of the full area of the picture. This preview effect can be misleading interlaced graphics are not faster-loading than non-interlaced graphics, they just look as if they download faster because the rough preview comes up faster..."
<--- end of quote --->