Many different types of graphic file formats exist, but three graphic file formats are generally used in web pagesGIF, JPEG, and PNG. Currently, GIF and JPEG file formats are the best supported and can be viewed by most browsers.

PNG files are best suited for almost any type of web graphic due to their flexibility and small file size; however, the display of PNG images is only partially supported in Microsoft Internet Explorer (4.0 and later browsers) and Netscape Navigator (4.04 and later browsers). So unless you are designing for a specific target audience using a browser that supports the PNG format, use GIFs or JPEGs for broader appeal.

GIF (Graphic Interchange Format) files use a maximum of 256 colors, and are best for displaying noncontinuous-tone images or those with large areas of flat colors, such as navigation bars, buttons, icons, logos, or other images with uniform colors and tones.
 
 

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