what is the amount of mAh of a standard usb cable?...?

Answer 1

mAh is the abbreviation for Mili Amp Hour, which means the amount of current (in milliamps ) a supply can supposedly deliver over a one hour amount of time.

USB provides a 5 V nominal at a +- of 5.25 thru 4.35.

Initially, a device can draw 100 mA. It may request more current from the upstream device in units of 100 mA up to a maximum of 500 mA. In practice, most ports will deliver the full 500 mA or more before shutting down power, even if the device hasn't requested it or even identified itself. If a (compliant) device requires more power than is available, then it cannot operate until the user changes the network (either by rearranging USB connections or by adding external power) to supply the power required.

Answer 2

A mAh specification does not apply to a usb cable or port. mAh is a measure of a batteries capacity in terms of how much current it can supply over a period of time. If a battery is rated at 1000 mAh it can supply 1000ma for one hour or 500 ma for two hours or 2000 ma for 1/2 hour, etc.
A usb port can deliver current indefinitely as long as it's host is turned on. A more appropriate question is: how much power (in Watts) can a usb port supply which has been answered previously.