javascript mozilla compatibility

hi 
my (java script)code for getting values from gridview to text box works well in crome,ie, but it dosent work in mozilla i dont know how to resolve this problem please help me.

code

this code gives me value of first cell of grid view in teacher_ID

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

this code runs well in all browser but not in mozilla
what to do please help