In the early days of the Web, Netscape decided on 216 colors to form the official "web-safe" color palette; this set of colors was subsequently adopted as the official technical standard across the Web. Under reduced color display conditions (monitors using only 256 colors on the Macintosh, or 1000's of colors (High Color or less) on Windows machines), Netscape Communicator and Internet Explorer will revert to this "web-safe" color palette for displaying everything in the browser window, whether graphics, backgrounds, or text. Under reduced color conditions, any color which is not web-safe will change into its closest web-safe color approximation, either by using two web-safe colors dithered together, or by wholesale conversion to a single similar color.
Under full 24-bit color conditions (millions of colors), this forced color conversion does not occur. However, many users do not have full 24-bit color monitors, either because they're using laptop computers, have extremely large monitors without adequate VRAM or computing power, or because they're using cellphones or other unusual web-browsing devices; because of this, it will be important to design websites using web-safe colors for some time to come.
The web-safe color palette was created by engineers (notice its numerical regularity!), not by graphic designers. As a consequence, it is rich in vivid, primary colors, but lacks subtle earth-tones and many so-called "corporate" colors. You won't find paper-shades, taupe, ecru, variations in off-white, or other subdued colors so popular in the print world. The web-safe color palette is the reason that web design has become known for vivid, jewel-tones and bright, garish color combinations.
That's not to say that you can't use other, non-web-safe colors in your designs; you must simply use those non-web-safe colors with extreme caution, and test the results under reduced color display conditions on all platforms.
Copyright © 2001 Michael Masumoto. All Rights Reserved.