Animation, GIF 89a can be used to create animations. JPEGs contain 24-bit color information. Photographic images are best saved as JPEG files because they offer better image quality packed into a smaller file. JPEGs offer a variety of compression levels. PNGs are cross-platform and compressed.
Quality is lower, images tend to look more grainy or pixelated.
But unfortunately, that's just the nature of images on the Web. Although 72ppi is the standard, monitor resolutions can much higher. A graphic appears to be about one inch square on a 72ppi monitor, but may actually appear quite smaller on a monitor with a resolution closer to 100ppi. Image Size Image size should be measured in pixels not inches because the actual size of the image is monitor dependent. File Size Keep your file size as small as possible.