Shifting to Web-safe colors
To protect colors from dithering in a browser, you can shift the colors to their closest equivalents in the Web palette. This ensures that the colors won't dither when displayed in browsers on either Windows or Macintosh operating systems capable of displaying only 256 colors.
To shift colors to the closest Web palette equivalent:
- Select one or more colors in the optimized image or color table. (See Selecting colors.)
- Do one of the following:
- Click the Web Shift button
in the Color Table palette. - Choose Shift Selected Colors to Web Palette from the Color Table palette menu.
The original color appears at the upper left of the color swatch and the new color at the lower right. The small white diamond 
in the center of the color swatch indicates that the color is Web-safe; the small square at the lower right of the color swatch indicates that the color is locked.
To revert Web-shifted colors to their original colors:
- Select a Web-shifted color in the color table and click the Web Shift button in the Color Table palette.
- To revert all Web-shifted colors in the color table, choose Unshift All Web Shifted Colors from the Color Table palette menu.
Do one of the following:
To specify tolerance for shifting colors automatically to the closest Web palette equivalents:
In the Optimize panel/palette, enter a value for Web Snap or drag the pop-up slider. A higher value shifts more colors.
(In ImageReady, click the Show Options control 
on the Optimize palette tab or choose Show Options from the Preset pop-up menu in the Optimize palette to view the Web Snap option.)