Display Tooltip in ASP.Net AJAX TabContainer TabPanel

You can set the ToolTip property

<cc1:TabContainer ID="TabContainer1" runat="server" ActiveTabIndex="0">
       
            <cc1:TabPanel ID="TabPanel1" runat="server" HeaderText="TabPanel1" ToolTip = "Tooltip_TabPanel1">
                <ContentTemplate>
                 Tab 1
                </ContentTemplate>
            </cc1:TabPanel>
            <cc1:TabPanel ID="TabPanel2" runat="server" HeaderText="TabPanel2" ToolTip = "Tooltip_TabPanel2">
                <ContentTemplate>
                   Tab 2
                </ContentTemplate>
            </cc1:TabPanel>
                      
            <cc1:TabPanel ID="TabPanel3" runat="server" HeaderText="TabPanel3" ToolTip = "Tooltip_TabPanel3">
                <ContentTemplate>
                  Tab 3
                </ContentTemplate>
            </cc1:TabPanel>
        </cc1:TabContainer>