What are is best??for sexing kittens

Hi I have looked at my 3 kittens who are now 3 days old , It looks like we have one girl and 2 boys but what is the best age to sex them and be 100% accurate

This may help

http://www.kitten-rescue.com/sexing_the_kitten.html

This site has photo's which should help

http://www.mystic-tree.com/kitten_sexing_guide.htm

Thanks guys, i think i have it right by the looks of those pictures

It's tough to see the difference if you have only male or female kittens, but if you have two of different sexes it's pretty easy to see the difference. Your best guess is probably correct. The easiest difference to see is that the anus and urethra are much closer together in the females and farther apart in the males.