Arduino uno:: Error occured on upload sketch

hi guys,
i need a help to solve an error occured while uploading sketch

Reading | ################################################## | 100% 0.06s

avrdude: verifying ...
avrdude: verification error, first mismatch at byte 0x0000
0x62 != 0x0c
avrdude: verification error; content mismatch

please help me!!!!