browser compatibility

Question

hi my web application works well with ie,crome but it dosent execute java script code on mozilla
so please help me for mozilla browser compatibility

my this function dosent work in mozilla.in this function i get the values(cells[0]) in userid from my gridview  can you help me why this functon dosent work in mozilla it works in crome,ie

  function assignValue(rowIndex) {

           User_ID = document.getElementById("<%=GridViewUsers.ClientID %>").rows[parseInt(rowIndex)].cells[0].innerText

       }