Hello,
You can do like this
<div style="height: 260px; width: 470px; overflow: auto; vertical-align: top;">
<asp:DataGrid ID="dgAPVender" AccessKey="G" runat="server" CssClass="clsGrid" BorderColor="Desktop" CellPadding="3" AutoGenerateColumns="False" Width="450px">
</asp:DataGrid>
</div>