Wash and cube potatoes into bite-sized pieces.
Boil water in large pot over high heat.
Add cubed potatoes to boiling water carefully.
Cook for 12-15 minutes until fork-tender.
Drain potatoes and let them cool completely.
Mix mayo and mustard in large bowl.
Add chopped eggs, celery, and onion pieces.
Stir in fresh dill, salt, and pepper.
Add vinegar and mix everything gently together.
Fold in cooled potatoes without breaking them.
Refrigerate for 2 hours before serving cold.