can't upload sktch

Arduino: 1.6.4 (Windows 7), Board: “Arduino Uno”

Sketch uses 6,266 bytes (19%) of program storage space. Maximum is 32,256 bytes.

Global variables use 479 bytes (23%) of dynamic memory, leaving 1,569 bytes for local variables. Maximum is 2,048 bytes.

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x7a

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x7a

avrdude: stk500_recv(): programmer is not responding

Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x7a

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x7a

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x7a

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x7a

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x7a

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x7a

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x7a

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x7a

This report would have more information with
“Show verbose output during compilation”
enabled in File > Preferences.

anybody knows whats the reason for this???

Is seems your computer is having problems communicating with the board.

Please do the following and let me know the outcome

  1. Try a loop-back test to ensure the communication between board and computer is functional.

  2. Try to manually reset the board while uploading. To do this you will press and hold the reset button on thw board before clicking upload. You will need to hold it until the IDE reports the size of the sketch.

  3. Reset the board, observe and describe the behabiour of the onboard "L" led.