Uses for GIF and JPEG files
Now that Netscape and other browsers are supporting both GIF and JPEG graphics in inlined Web page images you could use either graphic format for the visual elements of your Web pages. However, in practice most Web developers will continue to favor the GIF format for most page design elements, and choose the JPEG format mostly for photographs, complex "photographic" illustrations, medical images, and other types of images where the compression artifacts of the JPEG process do not severely degrade image quality.
Advantages of GIF Files
The most widely supported graphics format on the Web
Advantages of JPEG Images