That's the 100 Ohm resistor, step 21.
Did you successfully switch the screen on at step 12? If not, you should have stopped and got it working first.
You'v got lots of solder on the pins of the female header (that the screen attaches into). Check all your solder points to ensure none have joined to another one.
Also, check the atmega-328 chip is positioned correctly in the socket and none of the pins are bent.