Not sure if this is what you are looking for.
<asp:LinkButton ID="lbAccept" runat="server" onclick="lbAccept_Click"
OnClientClick="return confirm('Are you sure you want to accept this ?')"
ForeColor="Yellow" Font-Bold="True" style="font-size:18px">I Accept</asp:LinkButton>
This is just a simple link button that will show confirmation dialog box when user clicks on it and if user choose Yes then server side lbAccept_Click will be executed.