Continuity mistake: Young Evan puts the cigarette on the fuse of the blockbuster, and as Lenny walks away the butt is shorter than when Lenny stands up near the mailbox, after tying his shoe lace. (00:12:25)
Continuity mistake: When Evan and his mom came out from the psychic, she confessed to Evan that she had two stillbirths before Evan. But during the last scene, when baby Evan was trying to kill himself, we hear a different dialogue saying that his mom had three stillbirths before getting him. (00:42:26 - 01:52:09)
Continuity mistake: While Evan talks to the "prostitute Kayleigh", the piece of pie on the table changes position between the shots.
Continuity mistake: After Kayleigh's suicide, Evan travels back to time to the part when he's in Mr. Miller's basement. When young Tommy appears on the steps, he leaves a small opening on the door, but when Mr. Miller argues with him about keeping the door shut, you can see that the door is wide open, which it wasn't in the shot before.
Continuity mistake: In the original junkyard scene Kaylee is wearing a completely different outfit than later on when Lenny kills Tommy. The first scene she is wearing two shirts and some high waisted, ill fitted jeans. Then when Lenny kills Tommy she's wearing a bright blue with white stripes spaghetti strap shirt and tight, well fitted jeans. Plus, a lot of the points of time travel change throughout the movie. In the original junkyard scene they have already made it to Tommy and Kaylee has been hit by the board before Evan has his blackout. When Lenny kills Tommy they're still walking through the junkyard. It could be argued that it has to do with where he started reading from the journal but the blackouts from his childhood are predicated on his future trips into the past. So he should have blacked out before he ever made it to Tommy.
Suggested correction: It's safe to assume that the basement incident and probable continued abuse in the first timeline destroyed Kay-lee's self worth, image, and esteem. In a world where that never happened, she would definitely at least of been dressing differently (the point would have been better illustrated had her hair been different too). As for the second part, I'd have to agree, unless in Evan going back the first time he changed the day Tommy decided he wanted to kill Crockett, this changing the exact day of the blackout. And changing what Kaylee was wearing, I guess.