Continuity mistake: The nurse changes position in the church.
Continuity mistake: After the prologue, you see the Montague boys in the yellow car. If you look at the Montague sitting in the back of the car, you can see that his sunglasses are on his forehead; a few seconds later he puts the glasses down over his eyes. In the next shot, his glasses are back on his forehead again.
Continuity mistake: Tybalt's tattoo changes constantly. When he's watching Mercutio dying on the beach, it's a plain simple heart on his chest. When Abra is forcing him to run away to his car (in the same scene) it is not there at all. Then when Romeo is chasing him in his car and Tybalt's car rolls over, as he crawls out, it is much more intricate, with black lines and fire. It also changes when he gets shot over the fountain.
Continuity mistake: In the beginning of the film, when we see the Montague boys in the car, the bald one has an uncoloured tattoo, but it's coloured yellow later in the film.
Continuity mistake: When Romeo and his friend drive to the church where Juliet lies. You see that their car is very dirty. But when they arrive at the church the car is all clean. It seems a little strange to clean the car, when they have to hurry, and he was wanted by the police.