My problem solved.
In the following code:
<asp:ImageButton ID="ImageButton3" runat="server" ImageUrl="~/menu7.gif" onMouseOut="MM_swapImgRestore()"
onMouseOver="MM_swapImage('ImageButton3','','menu_7.gif',1)" AlternateText="onmouse"
ToolTip="onmouse" PostBackUrl="" meta:resourcekey="ImageButton3Resource1" /
>
In the MM_swapImage() function that is called for onMouseOver' event , instead 'ImageButton3' must be 'ctl00_ImageButton3':
<code><pre lang="vb"><asp:ImageButton ID="ImageButton3" runat="server" ImageUrl="~/menu7.gif" onMouseOut="MM_swapImgRestore()"
onMouseOver="MM_swapImage('ctl00_ImageButton3','','menu_7.gif',1)" AlternateText="onmouse"
ToolTip="onmouse" PostBackUrl="" meta:resourcekey="ImageButton3Resource1" /</pre>
></code>
Best regards,
Nima