Arduino Uno : Unable to upload programs

Binary sketch size: 2970 bytes (of a 32256 byte maximum) avrdude: verification error, first mismatch at byte 0x0000 0x0c != 0x00 avrdude: verification error; content mismatch

it was working fine but this error just cropped up ; i m unable to upload any programs into the arduino

Please do not cross-post.