The following code will solve your issue.
protected void gridview1_RowDataBound(object sender, GridViewRowEventArgs e)
{
e.Row.Cells[0].Visible = false;
}
but take a look at the below code, because it have an advantage, also this hides the column you mentioned & you can get the value from that 1st column at run time. so i prefer this for you.
protected void gridview1_RowDataBound(object sender, GridViewRowEventArgs e)
{
e.Row.Cells[1].Attributes.Add("style", "display:none");
}