I hope this helps... I found it at the following url:
http://www.techbase.iofm.net/tips/applemac/tip1.htm
On an iMac, Blue and White G3, Power Mac G4 (PCI Graphics), and PowerBook G3 Series (Bronze keyboard):
1 beep = No RAM installed/detected.
2 beeps = Incompatible RAM type installed.
3 beeps = No RAM banks passed memory testing.
4 beeps = Bad checksum for the remainder of the boot ROM.
5 beeps = Bad checksum for the ROM boot block.
On a Power Mac G4 (AGP graphics):
1 beep = no RAM installed.
2 beeps = incompatible RAM types.
3 beeps = no good banks.
4 beeps = no good boot images in the boot ROM (and/or bad sys config block).
5 beeps = processor is not usable.