The first digit assigned to all Visa cards is four, and the second through sixth numbers are connected to the financial institution. Then, either the seventh through 12th numbers, or the seventh through 15th, are the account number, while that final 13th or 16th digit is the check number.
Limited color, Lossy format, small file. GIF(Graphics Interchange Format) is limited to an 8-bit palette, or 256 colors. This makes the GIF format suitable for storing graphics with relatively few colors such as simple diagrams, shapes, logos and cartoon style images.
Smallest image format. What is the smallest (file size) image format that is out there right now? When you say image do you mean like logos, banners etc? If so, most people save them in a .gif format, as it keeps the quality the best and is generally the smallest size. For actual pictures, you'd be better off saving them in .jpg format as that format keeps better quality for pictures.