Web graphic file types
GIF
Short for Graphical Interchange Format. GIF-format graphics are used for most Web graphics. They are limited to 256 colors, but remain sharp.
JPG
Short for Joint Photographic Experts Group. JPG-format graphics are used mostly for photographs. They include millions of colors, but get blurrier each time they're saved.
PNG
Short for Portable Network Graphics. PNG-format graphics combine some of the features of both GIFs and JPGs, but aren't used much because GIFs and JPGs work fine for most applications.