.gif 
The most logos, cartoons, and simple line graphics on the Web are now in GIF format, and all Web browsers that support graphics can display GIF files. GIF files incorporate a compression scheme to keep file sizes small.

GIFs are limited to 8-bit (256 or fewer colors) color palettes.

ANIMATED GIFs: The GIF file format allows you to combine multiple GIF images into a single file to create animation. There are a number of drawbacks to this functionality, however. The GIF format applies no compression between frames, so if you are combining four 30-kilobyte images into a single animation, you will end up with a 120 KB GIF file to push through the wire.

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 .jpg 
Joint Photographic Experts Group (JPEG) compression scheme. JPEG images are very populas with graphic designers, photographers, artists, medical imaging specialists, and other groups for whom image quality is paramount.

The more you squeeze a picture with JPEG compression, the more you degrade its quality. JPEG can achieve incredible compression ratios, squeezing graphics down to as much as one hundred times smaller than the original file.

 .png 
Portable Network Graphic (PNG, pronounced "ping") is an image format developed by a consortium of graphic software developers as a nonproprietary alternative to the GIF image format. PNG graphics were designed specifically for use on Web pages, and they offer a range of attractive features that should eventually make PNG the most common graphic format.

These features include a full range of color depths, support for sophisticated image transparency, better interlacing, and automatic corrections for display monitor gamma. PNG images can also hold a short text description of the image's content, which allows Internet search engines to search for images based on these embedded text descriptions.

Unfortunately, the PNG graphic format is not yet widely supported, and the current implementation of PNG graphics in the major Web browsers does not fully support all of PNG's features.