Customize Denial Notification Page on TMG 2010

I have custom HTML code that I entered into TMG 2010 configuration to be displayed to users as a denial notification  when accessing non-business related web sites. but it's not  working.

Through configuration process I  replaced this file with the one already located at  %programfiles%\Microsoft Forefront Threat Management Gateway\ErrorHtmls, called 12232.htm

When I open the file on the server it works fine ,but nothing appears on client's screen except blank page with corrupted file sign on the top.

HTML file includes JPG image which also located on the same folder .

I want to know what should be done to ensure display this image on clients screens .

Thanks in Advance,

Regards