Continuity: At the wedding the bride lifts up her arms to hug someone and you can clearly see that there are rips in the armhole of her dress (which aren't supposed to be there
Great sites
The Best Man mistakes
Continuity: When all four of the guys are sitting around a table playing cards and they're talking about marriage, one of the guys gets really mad and pushes the table and tries to strangle the guy at the other end of the table. All of the cards and even a bagel that were sitting on the table go flying off. But then when he calms down and sits back down, the table is perfectly in place, and the cards and bagel reappear as if they never flew off.
Continuity: During the wedding rehearsal scene, Mia asks to speak with Harper alone. When she kisses him, the same movements and kiss are repeated back to back.