Continuity mistake: When Lynette is at the school, the teacher is waiting outside eating. If you look at her hands, you can see that she has a white napkin. The napkin changes from one hand to the other between shots, and in one shot it is small and the other it is not.
Continuity mistake: At one point in episode 1.2 ("Ah, But Underneath"), Susan looks at the note used to blackmail Mary Alice and we can see that it has been folded twice and become somewhat crumpled. Two episodes later in "Who's That Woman?" (1.4) when the girls show the note to Paul, it is almost perfectly smooth with a single horizontal crease.
Continuity mistake: When Bree goes to see Zak, in one shot her hands are intercrossed, then in the next her arms are crossed. (00:17:55)
Running to Stand Still - S1-E6
Continuity mistake: In one shot during the poker scene the baby moniter changes position to the other side of Lynette then back again. (00:13:30)
Running to Stand Still - S1-E6
Continuity mistake: When Lynette is talking to Jordana the items on the table keep changing position in between shots. (00:29:30)
Running to Stand Still - S1-E6
Continuity mistake: When Bree goes over to talk to Dr. Goldfine in the restaurant, she puts her napkin on top of her plate, but when she sits back down, she takes it off of her chair.
Continuity mistake: When Bree sees the presents that Rex has bought for the children, she walks up to the car. As she stops walking you can see her hair particularly on her left side is being blown gently by the wind and continues to be blown through most of the shot. In the following shot her hair is now sitting perfectly without any wind blowing it.
Continuity mistake: When Bree, Susan and Lynette are scrubbing the road, a red sports car zooms past them. Lynette stands, hurls abuse and throws her scrubbing brush at the car which can be seen bouncing off the car and down the road. She then kneels down and continues to scrub with the brush.
Continuity mistake: As Susan tries to get the dog to help the second time you can see the towel Susan tried to use to get the dog to help her. The shot then shows Susan and the towel has disappeared. After a quick shot of the dog it cuts back to Susan and the towel has reappeared.
Continuity mistake: When Bree gets out of the golf cart to see Rex on the field, she is carrying a pot of urine in her left hand, but in the next shot, of her upper torso and face, her left hand is clutching the strap of her handbag and the pot is now in her right hand.
Continuity mistake: When Lynette is sitting on the bench chatting to Claire in the park, you can see that Lynette has her hand on the pram, but when the camera angle is behind Lynette in other shots, she no longer does.
Continuity mistake: When Lynette sits down next to Claire on the bench at the park, Claire is wiping her hands with a tissue. Claire is not wiping her hands in the next shot, but in the shot after that, she is.
Continuity mistake: When Lynette introduces herself to Claire at the park, the strap on her handbag is on her shoulder. When the camera angle changes to behind Lynette in the next shot, the strap has gone, and in the shot after that, it is back again.
Continuity mistake: When Zach is in Julie's bedroom, he says to her, "And they buried her, to protect me" and you can see that Zach has his hand on his cheek. When the camera angle changes to behind Zach in the next shot, he no longer does.
Continuity mistake: Before the fight between Helen and Susan at the fashion show, Susan has a flower in her hair. There is no sign of the flower when Helen tears off part of her wedding dress, but when Susan says "What?", the flower is back again.
Continuity mistake: When John is speaking to Susan about his relationship with Gabrielle, Susan puts her hand on John's cheek, but in the next shot, when John's mother is looking out of her car, Susan can be seen with her hand on John's shoulder.
Continuity mistake: In the scene where Bree and Lynette are talking about nannies, Lynette is in the back seat strapping her baby daughter into the car seat. In the shot facing Bree, Lynette takes a baby toy lying on the back seat and hands it to her daughter, but in the next shot facing Bree, the toy is back on top of the seat where again Lynette hands it to her baby.
Continuity mistake: When Bree is about to leave the hospital she picks her bag up with her left hand to put it on her right shoulder but when the camera angle changes she's put the bag on her left shoulder with her right arm.
Continuity mistake: When Bree is talking to Mike in hospital, the position of her roll neck jumper on her right shoulder changes constantly throughout the scene. In some shots it's rolled down, in some it is rolled up.
Every Day a Little Death - S1-E12
Continuity mistake: Bree arrives home carrying a package in her left hand and bags in her right. In the next shot, when her phone rings, the package is gone, the bags are in her left hand and she answers the phone with her right. (00:07:10)
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.