While the more common decimal system uses a base of ten to represent all possible numbers, hexadecimal notation uses a base of sixteen: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, A, B, C, D, E, F. While such a system may seem confusing at first, it works extremely well in computing environments. For example, a single byte of information can be represented as eight bits (10011101), decimal numerals (913), or simplified to hex (9D). In hex, every byte can be shown as two hexadecimal characters.
As it relates to Web design, hexadecimal is the alphanumeric system used to specify colors in HTML. For example, the hexadecimal equivalent of white is FFFFFF, while black is 000000.