To dither or not?

[Paul]

In CS2 imagemaker, when saving a gif file you have choices, whats the difference between dithered and not dithered please?
And when/where would you use these differing types of saved file.
Thanks.

 

[dv8_fx]

To understand dithering.... What Is Dithering in Photoshop? | eHow.com

If you want a smaller file size for ease of loading in the web, dithering helps.

 

[MichleJohn]

Unless you are using "real" color table option, otherwise the color table may not contain all the colors used in the image. To simulate the color of the color table is not, you can use dithering. Dither color mixing existing pixels to simulate the missing colors. Select the menu dithering option and enter the number of dithering value. The higher the value, the more the color of the imitation, but may increase file size. Dither from the following options: are all dither, but the use of the color closest to the lack of color. This often led to the shadow color of the image between the sudden change, and cause color separation. Diffusion using the error diffusion method to produce than the "pattern" option structure is more loosely dithering. To prevent the image contains the color of the color table entry to be fake color, should select the "Keep the actual color." This Web images on the storage of fine lines and text very useful. Halftone pattern using a similar simulation of the square pattern in the color table without any color. Noise helps reduce edge image slice joint patterns. If you plan to cut hours to be placed in the HTML table of images, should select this option.