The ScrollBars property enables you to display scrollbars around a panel : Panel « ASP.net Controls « ASP.NET Tutorial

<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

    void Page_Load()
    {
        for (int i = 0; i < 100; i++)
            bltList.Items.Add("Item " + i.ToString());
    }

</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <style type="text/css">
        html
        {
            background-color:silver;
        }
        .contents
        {
            background-color:white;
            width:200px;
            height:200px;
        }
    </style>
    <title>Panel ScrollBars</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>

    <asp:Panel
        id="pnlContent"
        ScrollBars="Auto"
        CssClass="contents"
        Runat="server">
        <asp:BulletedList
            id="bltList"
            Runat="server" />
    </asp:Panel>

    </div>
    </form>
</body>
</html>

3.20.Panel
	3.20.1.	Important properties, methods and events of Panel control
	3.20.2.	Use asp:panel to host asp.net controls
	3.20.3.	The ScrollBars property enables you to display scrollbars around a panel
	3.20.4.	The Panel control enables you to work with a group of ASP.NET controls: show or hide
	3.20.5.	Set AssociatedControlID for asp:Panel
	3.20.6.	Hide, show panel