where to write content page script in master.aspx or webform

Iam trying to fit gridview in horizontal and vertical scroll bars like below but its not getting..how to code it?

<%--Div contains the new header of the GridView--%>

<%--Wrapper Div which will scroll the GridView--%>

width: 600px; height: 300px;" onscroll="Onscrollfnction();">

BackColor="White" BorderColor="White" BorderStyle="Ridge" BorderWidth="2px"

CellPadding="3" CellSpacing="1" GridLines="None"

onrowcommand="gridCustomer_RowCommand"

onrowdatabound="gridCustomer_RowDataBound">

<%#Container.DataItemIndex + 1%>

//code behind side

protected void Page_Load(object sender, EventArgs e)

{

if (!IsPostBack == true)

{

gridCustInfoBind(1);

if (gridCustomer.Rows.Count > 0)

{

ClientScript.RegisterStartupScript(this.GetType(), "CreateGridHeader", "");

}

public void gridCustInfoBind(int pageIndex)

{

try

{

//open the db connection if it is closed...

if (connection.State == ConnectionState.Closed)

connection.Open();

command = new SqlCommand();

command.CommandText = "sp_Get_CustInfoSerach";

command.CommandType = CommandType.StoredProcedure;

command.Connection = connection;

command.Parameters.AddWithValue("@PageIndex", pageIndex);

command.Parameters.AddWithValue("@PageSize", int.Parse(ddlPaging.SelectedValue));

command.Parameters.Add("@RecordCount", SqlDbType.Int, 4);

command.Parameters["@RecordCount"].Direction = ParameterDirection.Output;

SqlParameter outParam = command.Parameters.Add("@bal", SqlDbType.Float);

outParam.Direction = ParameterDirection.Output;

SqlDataAdapter daAcc = new SqlDataAdapter(command);

DataSet dsAcc = new DataSet();

daAcc.Fill(dsAcc);

IDataReader idr = command.ExecuteReader();

gridCustomer.DataSource = idr;

gridCustomer.DataBind();

ClientScript.RegisterStartupScript(this.GetType(), "CreateGridHeader",

"");

idr.Close();

connection.Close();

}

catch (Exception ex)

{

lblMessageCustSerach.Text = ex.Message;

lblMessageCustSerach.Visible = true;

}

finally //Close db Connection if it is open....

{

if (connection.State == ConnectionState.Open)

connection.Close();

}