Why ImageButton control does not show proper coordinate value?

<asp:Label ID="Label1" runat="server" Text=开发者_运维技巧"Click Image Button"></asp:Label><br />
<asp:Label ID="Label2" runat="server" Text="See The Co-ordinates"></asp:Label>
<br />
<asp:ImageButton ID="ImageButton1" runat="server" Height="100" Width="100" ImageUrl="~/DSC06427.jpg" onclick="ImageButton1_Click" />

In this two labels are added above the image but still the maximum value of image y co-ordinate is 100 Instead It should be 100+

Actually the co-ordinates are taken with respect to image corner not according to page thats why this occurs.