Margaret's legs are crossed left leg over right leg at 28 minutes into the movie. While Margaret and Mark are still talking an immediate camera angle is changed mid sentence and her right leg is now over left leg without opportunity for the change at 28:16.
(at around 1h 27 mins) When Margaret arrives at the pool, she is wearing socks. When she removes her shoes, the socks are gone.
When Margaret takes off her shoes at the pool there is nothing near them. In the next shot, her socks can be seen sitting beside them.
In the store scene, with him on the horse. One scene had the back of money facing out out the horse"s mouth. Then the front side of money. Then back to the backside of the money.
In the shot where Mark and his sister are playing music together, the sheet music on the music stand is upside down.
Right after the perfect moment with the angel wings, the dog appears and viewers clearly see Mark looking back at it through the reflection on the shop's windows.
At the end of the movie as Margaret and Mark pass through the sliding doors the numbers for the address can be seen in reverse in the glass as 27961, but when they get outside and the weather changes the building behind them shows the address as 13241.
There are only two types of eagles in the United States, Bald Eagle and Golden Eagle. The bird in the movie was neither a juvenile nor adult Bald nor Golden Eagle.
When Mark visits the animal shelter to find Margaret, he tells the shelter employee that he is "looking for a girl", to which the employee responds "We only have animals here". But Mark never indicated that he was looking for a human girl, thus his statement would have obviously been interpreted as looking for a female animal to adopt.
Margaret says that space shuttles are suborbital. This is not true. Suborbital flights never reach the speed to maintain low earth orbit.
In one scene Margaret is seen playing chess on her phone. She is playing as Black (though the board's position is upside down from her perspective). She plays the move 'Queen to b3', and the game announces 'Checkmate', giving her the win. However, the white king is not actually checkmated. White could easily play 'King captures Queen on b3' and continue playing. Margaret essentially blundered her queen for no reason.
Henry mistakenly refers to the bookstore Barnes & Noble as Barnes & Nobles. As this is the common vernacular, this could be considered the correct pronunciation by the character.