How to add the scroll bar to the div container?

See more:

C#

ASP.NET

Hi,
Here is the code i am using to display the notifications in my dashboard but if the notifications increases the scroll bar is not coming.So now i want to add the scroll bar to it.

<td style="width: 15%; vertical-align: top">
                                <table style="width: 100%; height: 330px; vertical-align: top">
                                    <tr>
                                        <td style="vertical-align: top">
                                            <div style="float: right" class="widgetContainerround">
                                                <div class="widgetHeader">
                                                    <div class="widgetheaderinner-left">
                                                        Notifications
                                                    </div>

                                                    <div class="clear">
                                                    </div>
                                                </div>
                                                <div class="NotifEventContainer" style="position: relative; overflow-y: hidden">
                                                    <usr:Notifs ID="Notifs1" runat="server" ShowPublic="True" ShowEventsOnly="False"></usr:Notifs>
                                                </div>

                                            </div>

                                        </td>
                                    </tr>

Can Anyone help me?