Continuity mistake: When Tom is proposing a toast to Lynette in the bar, he's holding the coffee with his left hand. However, in the next shot he's drinking the coffee with his right hand, and when the shot changes he's holding the coffee in his left again.
Continuity mistake: During the dinner scene, Ian starts to pour his mother some wine, but in the very next shot, he starts to pour it again.
Continuity mistake: Carlos swiped every thing from the table but a fork appears behind Edie. (00:18:35)
Continuity mistake: When Lynette sends Kayla upstairs, her bag is seen both on her shoulder and in her hand between shots.
Continuity mistake: When the boy paints "witch" on Mrs. McCluskey's front door, he holds the container in his left hand and the brush in his right. But when Karen gets out and he runs away with the other kids, the two items switch positions.
Visible crew/equipment: When Carlos is speaking to Charles (Travers' father) outside about joint custody and Charles says "Y'know, I just don't get it", a boom mic and pole are reflected in one of the windows near the front door of the house.
What Would We Do Without You? - S3-E22
Revealing mistake: When Lynette tears open Tom's shirt before making love to him, you can see there are already scratches on his chest before she scratches him.
Getting Married Today - S3-E23
Continuity mistake: Gabby's hair in the beginning has her bun high on her head and her tiara is visible from the front. When Bree walks in, and when she overhears Victor and his father talking, her tiara is farther back on her head and no longer visible from the front.
Answer: Kayla was sent away in episode 16 (The Gun Song) in season 4, after falsely accusing Lynette of child abuse. She now lives with her grandparents - probably Nora's parents.
I'm curious why we never see her again, why she never talked about, and why Tom never mentions visiting her.