In a perfect world, when you cat has a liter of kittens she will survive the birthing process and be a doting mother to her new babies. Sadly, this is not always the case, and on a regular basis many cat owners are faced with the distressing proposition of having to attempt raising a batch of kittens without the requisite knowledge. In examining kitten health in general terms, their survival is incumbent in large part to obtaining adequate nutrition on a consistent basis. There are numerous recipes available on the internet these days of replacement recipes for kitten milk, a few are excellent, others can be deadly.
To begin with, plain cow milk should never be given to any kitten, and neither should any preparation that uses mayonnaise. Kittens require taurine to thrive, and neither of these substances contain any taurine. Secondly, kittens have not yet developed a fully functioning digestive system, and recipes that use these foods may cause much greater harm than good. Always error on the side of caution in feeding kittens and don't believe everything you read - take your responsibility seriously when you have become the gaurdian of helpless creatures!
A commercial milk replacement is always better than anything you can make at home to feed kittens, but at times this is not always possible immediately. In the interim, a great replacement is to mix 3 egg yokes, 3 ounces of water, 3 ounces of condensed milk, and 4 ounces of plain unflavored yogurt thoroughly. If these ingredients are unavailable a replacement can be made from a few spoons of boiled chicken that is pureed and added to a few ounces of water to make a very, very soupy mix. Never prepare more than a 24 hour supply of replacement milk for kittens, and make certain it is stored in a refrigerator and warmed to a temperature of about 95 degrees Fahrenheit before using.
Feed a kitten very slowly while it is in a "stomach facing down" position, if fed too quickly a kitten may aspirate or drown, or have an issue with pneumonia. Remember, you are taking emergency measures - don't go crazy, you are just trying to keep the kittens alive until you can get appropriate food and professional guidance. In any situation where the mother cat is deceased or absent for an extended period of time, purchase a commercial milk replacement as soon as is possible, and get the kittens to a veterinarian. A vet can give you all of the information that is necessary to ensure the little ones will thrive and prosper, along with teaching a concerned human the skills to help.