you can put your gridview inside div as:
<div style="overflow:scroll; height: 50px; width: 50px">
<asp:GridView ID="myGrid" runat="server />
</div>
or in a pnel as:
<asp:Panel ID="scrollableGridArea" runat="server" style="overflow:scroll; height: 50px; width: 50px">
<asp:GridView ID="myGrid" runat="server />
</asp:Panel>