1) I want to know what exactly was bit confusing technique. If you can post a link to some datasheet or website. I will be very thankfull. 2) Also I want to know is the lock bit feature of Atmel AT89CXX series is foolproof or this also is crackable.
1) simply 'miswring the address and data lines to the ROM e.g D7 from the micro to D4 on the ROM etc.
2) the locks are efficient, but EEPROM can be defeated by opening the chip and microscopically checking it. Someone else will have to chime in on Flash. The most common oversight in 'locking' is that in many cases you can/could attach an external ROM and do movc. This can only be done with chips with less than 64k of internal ROM. Some of the modern chips have movc locks.

If the value of intellectual property of the code is high enough it can be cracked.

Erik