Where should a person keep his hand when offering his prayers.

I am a follower of the hanfi madhab and keep my hands just below my navel.this is the practice followed almost everywhere in india. However recently i read that you have approved that there is no Saheeh hadith supporting this act. please clarify.also i would be grateful if oyu could tell me whats the difference between a Saheeh hadith and other hadiths. Generally people here are of the view that a person can keep his hands below his navel or on his chest. I have also read this fact in my school book. Please clarify.