In HTML, colors are represented either as hexadecimal values ​​(such as #FF0000) or as color names (red). Web-safe colors are those that appear the same in Netscape Navigator and Microsoft Internet Explorer on both Windows and Macintosh systems when running in 256-color mode. The conventional wisdom is that there are 216 common colors, and that any hexadecimal value that combines the pairs 00, 33, 66, 99, CC, or FF (RGB values ​​0, 51, 102, 153, 204, and 255, respectively) represents a web-safe color.

However, testing has shown that there are only 212 web-safe colors instead of all 216 because Windows Internet Explorer cannot correctly render the colors #0033FF (0,51,255), #3300FF (51,0,255), #00FF33 (0,255,51), and #33FF00 (51,255,0).

When web browsers were first developing their look and feel, most computers could display only 265 colors (8-bit). Today, most computers can display thousands or millions of colors (16-bit and 32-bit), so if you are developing a site for users with current computer systems, there is no need to use the browser-safe palette.

One case where you would use a web-safe color palette is when developing sites for alternative web devices, such as PDAs and cell phone displays. Many of these devices offer only black and white (1-bit) or 256-color (8-bit) displays.