What should he do with the leftover donations?
Question

                A person collected an amount of money from the members of his website. He was surprised that the amount collected is very big. What should he do with the rest of this amount? Should he use it for whatever the website needs?.
Praise be to Allah.
    What he must do is ask permission from the donors to dispose 
    of it as he wants on permissible or recommended things. It is not 
    permissible for him to collect charity or donations in the name of a 
    specific cause then spend it on something else, unless he does not know the 
    identities of the donors and has no means of contacting them. In that case 
    he must spend that charity on the closest cause to that for which he 
    collected it. So if a person collects money to build a mosque, then there is 
    extra money, he should spend it on building another mosque, and he should 
    not spend it on the poor and needy, for example. 

    This is what the brother who asked this question should do. 
    If it is possible for him to tell the one who donated a large amount about 
    the situation, and ask his permission to dispose of it, then he should do 
    that. Otherwise he may spend it on the web site and buy what is needed for 
    it. 

    The scholars of the Standing Committee for Issuing Fatwas 
    were asked: 

    I collected donations to build a mosque in the village, and 
    the mosque was built. Some good people donated money to complete the 
    interior, because the money that I had left was not sufficient for that. I 
    have some of the donations left. Is it acceptable to spend the leftover 
    donations on building fences for the Eid prayer place and graveyard in the 
    village? Is it acceptable to spend the extra funds on buying air 
    conditioners or furnishings for mosques in other villages? Is it acceptable 
    to spend the extra funds on helping those who want to get married or on the 
    poor and needy in the village? All of that is with the intention of the 
    reward going to the donors. Please note that the donors include both 
    villagers and outsiders. 

    They replied: 

    It is permissible for you to spend the remaining money that 
    you have left over from building the mosque that you supervised on building 
    another mosque, if the first mosque does not need that. It is not 
    permissible for you to spend the money mentioned on anything other than 
    building or maintaining mosques, because that is spending it on something 
    other than the purpose for which it was donated. End quote. 

    Fataawa al-Lajnah al-Daa’imah (al-Majmoo’ah 
    al-Thaaniyah, 5/208). 

    And Allaah knows best.