I presume you mean a 23" (not 24") Apple Cinema Display?
If so, be aware that the Power Supply Units for different size Cinema Displays are not interchangeable.
A 23" unit ships with a 90W PSU, a 20" only with a 65W PSU.
A 90W PSU will work with both 23" and 20" Cinema Displays, but a 65W PSU will only work with a 20" Cinema Display.
I guess this will only help if you have a mixture of 20" and 23" CDs, and have been swapping them around. Both PSUs look nearly identical, which doesn't help. The Wattage is however written on the PSU somewhere.