Boil potatoes in skins until fork just goes through them; drain, cool and refrigerate until cold. (I refrigerate over night)
Mix together mayo, vinegar and sugar, set aside
Peel potatoes, cube into bite size pieces. layer them in a bowl, sprinkle with a little chopped onion, sprinkle with celery seed, a little sprinkle of salt and repeat layers until potatoes are gone. Pour dressing over layered potatoes and stir well. sprinkle with more celery seed (if you think it's enough it's probably not : )
refrigerate!! we think it's best refrigerated over night!