Most browsers versions being used today will support 16 bit color, allowing the default palette to be overridden. If no graphics card is installed or no higher bit selection is made for the graphics driver, only the colors contained in the default browser palette will be available.

Dithering and Non-Dithering Colors

If your system is set for 256 colors, the red square below will look speckled. That is because the color is not in the browser color palette. If the red square looks smooth, your system will display colors outside of the browser palette and allow you to enjoy all of the graphics on the Web as they were created.

Red color NOT in the default color palette. Does it look speckled?

If a designated color is not included in the default palette, the browser will choose two colors in the palette to closely replicate it. This substitution of color is called "dithering". That is why certain images may look speckled or grainy. Text will not be "dithered", but it will be displayed using the next color closest to it in the palette.

The chart below is a handy utility that contains the 216 "Non-Dithering" palette colors showing both the RGB and hexadecimal codes for each. While it is difficult to create more complex or shaded images using this limited number of colors, try using these "safe" colors for text, backgrounds and links first to see if they work for you. If not, go ahead and use colors outside the browser safe palette.

Take a look at the Browser Safe (Non-Dithering) Color Chart.

Most computers sold over the last several years display 65k colors,
so you are pretty safe NOT using only browser safe colors! :}