How to find gridview cell index or cell value

so many ways but as per requirement ...

1) in databound event : DataGridViewCell cell = this.dataGridView[e.ColumnIndex, e.RowIndex];

you can use this in for loop

2) string strFirstName = Grid1.Rows[3].Cells["FirstName"]

3) GridViewRow gRow = GridView1.Rows[RowIndex];

e.g.

for (int i = 0; i < grdMyGrid.Rows[0].Cells.Count; i++)
{
grdMyGrid.Rows[0].Cells[i].Width = Unit.Pixel(200);
}

in javascript

var n = document.getElementById("GridView1").rows.length;
            var i;
            for (i = 2; i <= n; i++) {
                tb = document.getElementById("GridView1_ctl0" + i + "_TextBox1");
                tb.value = i;
            }