Atmega328P-PU in Arduino Uno R3

Hi,

In one day a have need the microcontroller from my Arduino Uno in order to insert it in a custom board and I've programmed it with another Arduino uno as isp.It worked ok and every thing was ok but recently I wanted to use my board and I put the microcontroller back in his socket but it doesn't work with Arduino Ide anymore.When I pressed upload ,the rx led blinks once and after nothing happens and I am getting this error:

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x03
Problem uploading to board.

I have more atmega 328p-pu but if I programmed them out of the board ,they doesn't want to work anymore.What can I do?

Arduino needs the bootloader in ATmega. You have to upload the bootloader, because programming via ISP cause remove it. You can do this with another Arduino via ISP.

Thanks man,you helped me a lot.Have a nice day!