Hi try this:
<asp:image id="impPfimage" runat="server" generateemptyalternatetext="true" alternatetext="ADD PHOTO" xmlns:asp="#unknown">
/>
</asp:image>
<div class="popUpStyle" id="divPopUp" style="display: none">
<table class="fonttext">
<tr>
<td>
Change Picture
</td>
<td>
:
</td>
<td>
<asp:fileupload id="fuChangePic" runat="server" xmlns:asp="#unknown" />
</td>
</tr>
<tr>
<td colspan="3" align="center">
<asp:button id="btnSave" runat="server" text="Save" onclick="btnSave_Click" xmlns:asp="#unknown" />
<asp:button id="btnCancel" runat="server" text="Cancel" xmlns:asp="#unknown" />
</td>
</tr>
</table>
</div>
<ajax:ModalPopupExtender runat="server" ID="ModalPopupExtender1" TargetControlID="impPfimage"
PopupControlID="divPopUp" BackgroundCssClass="popUpStyle" PopupDragHandleControlID="panelDragHandle"
DropShadow="true">
</ajax:ModalPopupExtender>