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First, are you sure she abandoned them? Mother cats don't stay with their kittens. They spend hours a day hunting and roaming, but come back to nurse them throughout the day.
If you are going to hand raise them there are a few things you have to know. First, they will not eat if they are cold. Make sure you have them warm by providing a heat source. You can use a heating pad, but put a number of layers of towels between the heating pad and kittens and only put the pad in part of their box so they can move away from it if they get too warm. Also, kittens don't always have enough sucking power for a bottle. Sometimes you have to 'drip' the milk in their mouth, but do it slowly and make sure they are swallowing because you don't want to get it in their lungs. They should be feed every 2-3 hours.
Also, they do not go to the bathroom on their own. They will only go if they are stimulated by mom's licking. You need to take a warm, wet wash cloth and gently rub their bottom until they go. Do this at every feeding.
If they are just laying there and not able to eat you should warm them up and give them some corn syrup in case they have low blood sugar. I use just a drop of corn syrup on their tongue.
I hope that helps.