Hi,
The USB 1.0 Spec contains a cable length limit of 5 meters, a cable delay spec of 30ns and a supply voltage minimum at any USB socket of 4.4 volts.
Chapter 7 of the spec covers the electrical specifications of the USB signals and limits all cables of any length to 30ns prop delay. Since cable varies from 3 to 6 ns per meter prop delay the maximum cable length can be calculated to be 5 meters.
This is still true for USB2.0. Though most cheaper peripherals would not work at this length due to the timing issues. You can get A-A Active Extension cables that help slightly, but would only really get you to 5m.
If you need to go beyond 5m (WHY???), then the only practical solution is to employ the use of a separately powered USB hub in the middle of 2 5m cables (but expect the occaisional problem due to both noise and attenuation at that distance).
Cheers
Merv