That could mean a lot of things, but usually it has to do with the device signature not matching what is being passed to AVRdude. Make sure you have the correct board selected, and of course verify the connections are working well (particularly rx/tx aren't crossed). Also, if all fails try a fresh in stall of arduino or whatever it is you're using. This could fix issues with bad board files that could also cause this.
That could mean a lot of things, but usually it has to do with the device signature not matching what is being passed to AVRdude. Make sure you have the correct board selected, and of course verify the connections are working well (particularly rx/tx aren't crossed). Also, if all fails try a fresh in stall of arduino or whatever it is you're using. This could fix issues with bad board files that could also cause this.