Can anyone tell me what is the different between USB 1.0 and 2.0? it's becaz i always hear that some devices are not compatible with 2.0...

USB 1.0 devices are not compatible with USB 2.0. However USB 2.0 devices are backward compatible with USB 1.0. The difference is only the transfer speed. USB 2 is faster that USB 1

Does anyone know what the differences are between USB1.0 and USB1.1? I have been looking everywhere, and there is no reference to what changes were made!!

As I know, one difference is, that USB 1.1 can handle several devices at different speed (slow speed 1.5 MBit/s (e.g mouse) and high speed 12 MBit/s (e.g printer)). USB 1.0 can handle just devices with the same speed. If there are still other differences - I don't know!

USB 1.0's max speed is 1.5 mbps (megabitspersec, not megabytespersec), 1.1's max speed is 12 mbps and USB 2.0's max speed is a whopping 480 mbps. USB 2.0 devices are backward compatible with USB 1.0 and 1.1 ports, but the USB 1.0 and 1.1 devices are not compatible with the USB 2.0 ports because of the speed of the bus. Higher number (2.0, 1.1, 1.0) => backward compatible with lower number but not vice versa. In general the main difference is SPEED.