Where do we keep our hands during Salat? Where do we keep our hands after Ruku before Sajda? Please give me good Muslim world web sites.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad sallallaahu alayhi wa sallam is His slave and Messenger.

It is Sunnah for a praying person to place his hands on his chest while standing in prayer. There is no difference between his standing before Rukoo' (bowing) or after it. In a Hadeeth narrated from Waa'il Ibn Hujr  he said: "Once I prayed with the Prophet and he placed his right hand over his left one and upon his chest while he was standing." [An-Nasaa'i]

Abu Daawood and An-Nasaa'i also reported the same narration that had a different wording: "The Prophet put his right hand over the wrist and forearm of his left hand."

These narrations also point out that the Prophet used to put his hands on his chest while standing during the prayer. There is a narration reported by Imaam Taawoos which reads: "The Prophet used to place his right hand on his left hand then he used to put both of them on his chest." (Ibn 'Abdul-Barr).

As for the narration which is said to be from 'Ali that: "It is Sunnah in prayer to put the palm of one hand on the palm of the other hand and place them both below the navel", all the scholars agree that this is a weak narration and therefore not correct.

As for your second question concerning the position of hands after Rukoo', the praying person could either put his right hand on his left one over his chest or let them both down his body.
For more detail, please refer to the Fatwa 82578. 

Allaah knows best.